Best Full Size Mattress

If you’re a solo sleeper who tends to toss and turn, or you like having room to spread out your arms and legs, a full size mattress might be the perfect bed size for you. A full size mattress measures 54 inches by 75 inches, so it can fit in most bedrooms. It’s well suited to almost any single sleeper.

We’ve compiled our recommendations for the best full size mattresses. We included other buying considerations such as mattress type, sleeping positions, and firmness level.

Best Full Size Mattresses

Amerisleep’s most popular mattress model is the AS3, with a medium feel perfect for side sleepers and combination sleepers. The AS3 has a newer hybrid counterpart, the AS3 Hybrid, but we’ll be focusing on the original memory foam mattress.

A full size AS3 is currently $899, with free shipping to anywhere in the continental USA. Every Amerisleep mattress includes a risk-free 100-night sleep trial and a 20-year warranty. Amerisleep bears all costs for defective mattresses for the first 10 years, and then for the next 10 years, you pay a portion of the repair or replacement costs.

How Lying Down Feels

Customer reviews mention how much better they’ve slept since switching to the AS3, and how it’s greatly improved chronic pain they’ve dealt with. Some even saw improvements in their sleep and how they felt in the morning after their first night. Now wonder the word “comfortable” is the most recurring bit of praise in consumer reviews.

Inside the Mattress

The 12-inch AS3 has three layers of foam. All Amerisleep foams are certified by CertiPUR-US®, which means the foam was processed without toxic materials such as mercury, lead, formaldehyde, ozone depleters, and certain flame retardants.

The top layer is 3 inches of Bio-Pur® memory foam, a more eco-friendly, breathable, and responsive alternative to traditional memory foam. Amerisleep manufacturers replace certain petrochemicals with plant-based substitutes to make Bio-Pur®.

Next is the Affinity layer with HIVE® technology. HIVE® technology contains hundreds of hexagonal cutouts separated into five zones—your head, shoulders, back, hips, and feet. The cutouts under your shoulders and hips compress for more cushion, while the cutouts under your head, back, and feet provide support.

At the bottom is 7 inches of Bio-Core® foam, a supportive material that deters sagging to extend the mattress’s lifespan. Bio-Core® is partly why Amerisleep can offer such an extensive mattress warranty.

A soft cover encases the mattress, promoting airflow. Called Refresh fabric, this material is highly innovative, taking heat and transforming it into infrared energy, instead of simply moving it away for release.

You can bundle an Amerisleep mattress with an adjustable base for further discounts. Amerisleep’s adjustable bed includes two full-body massagers, under-bed lighting, USB charging ports, and wall-glide technology that keeps your nightstand within reach no matter how you position the mattress.

The mattress bundle includes white glove delivery, which means the delivery team will set up your new adjustable bed and haul away your old mattress.

The Zoma Mattress was designed to improve an athlete’s performance with a good night’s sleep, but you can sleep well on it regardless of how physically active you are. Lots of people commend the Zoma Mattress for greatly improving their pain whether they’re athletes, work physical labor jobs, or simply deal with chronic pain.

A full size Zoma Mattress is currently $599 and comes with a 100-night trial and a 10-year warranty. The warranty includes coverage for sagging deeper than an inch.

How Lying Down Feels

The Zoma Mattress possesses a medium feel designed to support recovery during rest. Sleepers won’t sink too far into the mattress’s surface, but the heavier parts of the body like the shoulders and hips will be gently cradled during the night.

Inside the Mattress

This 12-inch mattress has three foam layers. A breathable polyester-elastane cover encases the mattress. The cover stretches to create air channels as you move on it.

The comfort layer is 2 inches of gel memory foam with Triangulex™ technology. The contouring triangle cutouts relieve pressure points in the shoulders and legs, while the midsection provides support. The cutouts also improve airflow, working with the gel foam to keep you cool as you sleep.

The next layer is 2 inches of latex-like Reactiv™ foam. Reactiv™ is a high-density foam that lets the mattress respond faster to your movements, preventing you from feeling stuck in the mattress.

The base layer is 7 inches of Support+ foam, which maintains the mattress’s structure by deterring sagging.

The Zoma Mattress also comes in a hybrid variation, called the Zoma Hybrid. Rather than a Support+ layer, it contains pocketed coils and a thin foam base. Plus, it’s slightly softer than the standard Zoma Mattress.

SEE ALSO: Zoma Mattress Review

The Vaya Mattress was designed to offer bouncy support and pressure relief at an affordable price. It’s an all-foam mattress made for all sleepers who are looking to save some money. Plus, even for its great price, the Vaya Mattress is cooling and environmentally friendly. And despite being so affordable, customers say it’s just as great as their pricier mattresses!

A full size Vaya Mattress is $499. The mattress includes a 100-night sleep trial and a 10-year warranty. The warranty covers sagging greater than an inch.

How Lying Down Feels

A single sleeper lying down on the Vaya Mattress should find it difficult to tell apart from more high-priced mattresses. The surface is gently soft but balances responsive support with adaptable support.

Inside the Mattress

A Vaya Mattress has a simple two-layer design and stands 12 inches tall. The cover is a blend of rayon, spandex, and polyester.

The comfort layer is 3 inches of Vaya Comfort Foam, a latex-like foam that’s less dense than your typical memory foam. Vaya Comfort Foam eases pressure and is responsive enough to prevent you from feeling trapped in your mattress. The base layer is 9 inches of high-density foam that prevents sagging.

While the original Vaya Mattress is made entirely from foam, Vaya also offers the Vaya Hybrid. It features pocketed steel coils in place of a thick layer of foam, providing extra bounce and airflow to sleepers.

SEE ALSO: Vaya Mattress Review

Just because you’re choosing the smaller full size mattress doesn’t mean you can’t enjoy a luxury mattress. The Nolah Evolution 15 is one of the best options when it comes to affordable luxuries, and the bed’s cooling features can make it an absolute necessity for anyone prone to sleeping hot.

How Lying Down Feels

With three potential firmnesses, the exact feel of the Nolah Evolution can vary. But the materials remain consistent, all of them working together to establish a surface that stays cool to the touch.

Inside the Mattress

Unsurprisingly for a luxury mattress this thick, the Nolah Evolution contains a number of layers that work together to create a comfortable surface. Starting with the cover fabric woven for lasting coolness, working with the underlying cooling foams and breathable border gusset.

The cooling foam AirFoamICE™ also serves as the bed’s primary source of pressure relief. A supportive foam for added resiliency and a transition foam rests underneath the AirFoamICE™ layer.

The core of the Nolah Evolution 15 is a series of pocketed coils on a foundation of recycled fibers. The coils are zoned into three areas for more comfortable support. Foam surrounding the coils strengthen the sides for edge support.

Underneath the coils’ foundation is a non-skid fabric to keep the mattress from sliding. Along the sides of the mattress are handles for easier carrying.

SEE ALSO: Nolah Mattress Review

For sleepers who want to reduce their carbon footprint with their shopping choices, the Spindle mattress is often the way to go. Not only is it an organic latex mattress, but the mattress offers sleepers the nifty ability to re-arrange the interior layers. This changes the feel of the surface, allowing it to suit different sleep styles.

How Lying Down Feels

The Spindle mattress has no set firmness, but the latex remains consistently cool and buoyant regardless of how the layers are arranged. Whether sleepers choose a softer or firmer feel, the top layer of wool and cotton covering offer a touch of gentle cushion.

Inside the Mattress

The fabric covering the Spindle is organic cotton, certified by the Global Organic Textile Standard (GOTS). This material moves heat and moisture away from the body, remaining cool and dry.

Underneath is a layer of organic wool, certified by Oeko-Tex and GOTS. Not only does this material bolster the cotton cover, the wool also serves as the mattress’s flame barrier.

Below the wool barrier is the latex foam layers, individually encased. Spindle’s latex foam is aerated for extra breathability, helping heat escape faster. The latex foam is certified organic by the Global Organic Latex Standard,  Oeko-Tex, and GOTS.

Amerisleep’s softest hybrid mattress is the 14-inch AS5 Hybrid, an excellent choice for side sleepers who want a little luxury. Compared to the AS3 we mentioned earlier, the AS5 Hybrid has a truly soft feel, making it much softer. It also contains pocketed coils rather than having a foam base.

As previously mentioned, all Amerisleep mattresses include free shipping, a 100-night sleep trial and a 20-year warranty.

How Lying Down Feels

The sheer softness of the AS5 is what immediately strikes a sleeper when they lie down on the surface. The underlying materials, however, keep the plush feel manageable, ensuring that sleepers won’t sink too far into the bed.

One consumer reviewer called the AS5 “the best mattress around,” while another wrote that “I can’t imagine there being a bed better than this.”

Inside the Mattress

There are four layers in an AS5 Hybrid. A soft, breathable cover encases the mattress, letting air circulate through the bed. AS5 Hybrid customers mention how they never thought a soft bed could be supportive, but that this bed proved them wrong.

On top is 3 inches of breathable, responsive Bio-Pur® memory foam. Next is 2 inches of Active Flex, a bouncy material that prevents you from feeling stuck in your soft mattress. Not only that, but it makes this soft mattress an excellent option for plus-sized people.

Then, an 8-inch layer of pocketed coils is built to support the spine and maximize airflow throughout the bed. The coils are firmer at the sides of the bed to prevent you from rolling off of the mattress. At the bottom of the AS5 Hybrid is an inch of base foam for added support.

SEE ALSO: Softest Mattresses in a Box

Many shoppers haven’t lost their fondness for a traditional spring-style mattress, but some spring mattresses simply can’t match the comfort that an all-foam mattress provides. To go beyond the usual amount of comfort an innerspring bed offers, the Saatva Classic offers up a Euro top with special materials and pocketed coils sandwiched between this pillow top and the innerspring base.

How Lying Down Feels

Thanks to its two coil layers, the Saatva Classic has an impressively springy feel, regardless of a person’s chosen firmness. Yet the smallest of movements of a sleeper won’t spread across its surface, thanks to its motion-isolating materials.

Inside the Mattress

The Saatva Classic has four layers, all wrapped within an organic cotton cover. This fabric keeps heat and moisture moving away from the body for a cooler feel. Saatva treats the cotton with an antimicrobial  compound to better maintain the mattress’s freshness.

The primary comfort layers are the bed’s pillow top and an underlying, dense memory foam. Not only does the memory foam provide extra conformability, but it offers targeted back support to help sleepers wake up refreshed and recharged.

The next layer consists of pocketed coils, placed to create a responsive surface without the drawback of jarring motions when a partner moves around the bed.

While these pocketed coils are supportive, the true support core is the base of tempered steel coils. These coils are surrounded by foam rails for reinforced edge support.

It’s not uncommon for people to sleep hot and wake up prematurely as their body heat is absorbed by the mattress. Even if their body temperature doesn’t naturally run high, they may still sleep hot if they live in a warmer climate. When it comes to cooling mattresses, we recommend the multiple-layer system of the GhostBed Luxe to stay cool at night.

GhostBed includes a 101-night sleep trial and a 25-year warranty with the Luxe mattress.

How Lying Down Feels

The GhostBed Luxe lives up to its name with a luxurious surface that gently cradles the body. The surface is quick to yield to body weight, staying cool even as it enfolds a sleeper’s curves for complete pressure relief.

Inside the Mattress

The GhostBed Luxe has seven layers that bring the mattress to 13 inches of height, including the plush fabric cover. GhostBed overall rates the bed as medium-plush, so we largely recommend this mattress for side sleepers.

The first layer of the Luxe is the Ghost Ice fabric cover, with phase-change material for consistent coolness. Sewn into this cover is the second layer of cooling, airy fibers.

Third is a thin gel memory foam layer that bolsters the soft feel of the fibers and fabric cover. Underneath the pressure-relieving gel memory foam is a layer of Ghost Ice material to keep the mattress cool to the core.

A thick gel memory foam forms the fifth layer of the mattress, ensuring the mattress truly hugs the body for pressure relief. The next layer is Ghost Bounce material, a foam that melds aspects of latex and memory foam. Ghost Bounce responds quickly to movements while conforming to the body.

The seventh and final layer is a thick, sturdy base foam for sleeper support and overall mattress structure.

Many single sleepers love stretching out on a hybrid mattress, which buoys the body with its bouncy coils. One of our favorite hybrid mattresses is the Brooklyn Bedding Aurora Hybrid. While mattress comes in three firmness levels, we specifically recommend the soft and medium options for side and combo sleepers.

Purchase of a Brooklyn Bedding Aurora Hybrid with a 120-night sleep trial and a 10-year warranty.

How Lying Down Feels

The plush foam layers and pocketed coils with targeted support help the mattress feel supportive and conforming. The exact feel will depend on a sleeper’s chosen firmness, but all options provide a balanced mix of cushioning foams and adaptable springs

Inside the Mattress

Five layers make up the Brooklyn Bedding Aurora Hybrid, all wrapped in a mattress cover with a cooling surface infusion.

The first layer is copper-infused foam known as CopperFlex™. The foam top conforms to the body for pressure relief but firms up underneath the body’s heavier parts for support. Not only is copper a naturally cooling agent, but the material also keeps microbes out of the mattress.

The second layer of TitanFlex™ foam adds elastic responsiveness, and the soft version’s TitanFlex™ layer feels different than the medium option. The third layer inside the soft and medium mattress is gel swirl memory foam.

The fourth layer is the bed’s main support, pocketed coils arranged to provide pressure relief and support as needed. The foam base underneath reinforces the coils as they compress under weight.

SEE ALSO: Best Casper Mattress Alternatives

Who Should Sleep on a Full Size Mattress?

Full size mattresses are perfect for people who want the space to sprawl but live in a smaller bedroom—one that’s less than 10 feet by 10 feet. If you like to stretch out your arms as you sleep, a full size mattress gives you the room you need.

And if you have a smaller guest room, a full mattress can still provide a visitor with a comfortable night’s rest. It’s wider than a twin bed and better able to serve as a comfortable mattress for guests.

We must also mention who should not sleep on a full size mattress—namely, couples who want to share a bed. If you divide it in half, a full mattress provides each partner with about 27 inches of sleeping space. Even if you and your partner sleep close together, 27 inches of space is a tight squeeze. You may have difficulty falling asleep, or you’ll wake up as the other shifts in their sleep.

Couples need the space that a queen size mattress or larger can offer. Don’t worry if you’re shopping on a tight budget. There are plenty of high-quality queen mattresses costing less than $1000.

More Bed Sizes

Perhaps a full size mattress isn’t suited for your needs—maybe you’re looking for a smaller mattress for a child that’s leaving their crib behind, or you need the best mattress for a couple to share. If so, there are five other standard bed sizes to consider.

Twin

Measurements: 38 inches by 75 inches

A twin mattress is the smallest standard size. It’s well suited for children moving out of a crib or toddler bed or adult sleepers who need a mattress for a small bedroom.

Twin XL

Measurements: 38 inches by 80 inches

A twin XL mattress offers 5 more inches of legroom than a standard twin mattress. If you want your child to have a mattress that can accommodate growth spurts or are a tall adult sleeper, a twin XL mattress might be the perfect choice.

Queen

Measurements: 60 inches by 80 inches

A queen mattress is the most popular bed size, as it suits couples and single sleepers and fits into most budgets and most bedrooms. However, some couples may want a larger mattress and should look at a king or California king size mattress.

King

Measurements: 76 inches by 80 inches

A king mattress is the widest standard size available. It offers the most personal space for couples, or even for single sleepers who want the luxury of spreading out.

If you and your partner can’t agree on how firm your bed should be, consider a split king mattress. A split king is a king size mattress separated into two halves, each half the same size as twin XL mattress.

California King

Measurements: 72 inches by 84 inches

A California king mattress, also known as a western king, is the longest standard size mattress. It’s an excellent choice for couples who need extra legroom or single sleepers taller than 6 feet.

Other Mattress Buying Considerations

Doing research can simplify your mattress shopping, as you’ll know exactly what you’re looking for in your next mattress. Knowing the type of mattress you want, your favorite sleeping position, and the best firmness for you will make mattress comparisons easier.

Mattress Types

A mattress’s material contributes to its feel, costs, and expected lifespan. Every material comes with its pros and cons.

Memory Foam

Memory foam is a popular mattress material thanks to its conforming, pressure-relieving properties. When you lie down on a memory foam mattress, it responds to your heat and weight, molding around your body.

Memory foam is also one of the quieter mattress materials, with nothing creaking as you move. And if you share a memory foam bed with a partner, neither of you will be disturbed by the other’s movements, since memory foam absorbs motion at the point of impact.

The drawback to traditional memory foam is its heat retention, which can wake you if the mattress grows too hot. Many mattress companies add infusions such as cooling gel, graphite, ceramic, and charcoal to wick away body heat.

Memory foam mattresses can last 7 to 10 years, depending on the foam’s quality. You can find memory foam mattresses at almost every price point.

Latex

Latex conforms to the body for pressure relief, much like memory foam. However, unlike memory foam, latex is naturally cooler and firmer—some companies include an optional pillow top for a softer mattress.

There are two types of latex foam: natural and synthetic. Natural latex is made by harvesting rubber tree sap and whipping it into foam, while synthetic latex is made from organic chemical compounds.

Natural latex mattresses are often expensive because of production costs, but many shoppers find the price worth it as a natural latex mattress can last 15 or more years with care. Synthetic latex mattresses cost less, but they also have a shorter lifespan.

Innerspring

Innerspring mattresses, also called coil mattresses, remain popular through familiarity and wide availability—you can find an innerspring model at most mattress stores and many furniture stores. The construction is simple, with an interior coil layer sandwiched between foam or fabric cushioning.

Many owners are dissatisfied by how little pressure relief the traditional innerspring mattress offers. Some manufacturers add a Euro or pillow top to create a softer mattress—the difference between the two is that a pillow top mattress has the additional padding sewn on top of the mattress with a visible gap, while a Euro top is placed under the mattress cover for a uniform appearance.

The other drawback to an innerspring mattress is its lifespan. Many do not last more than five or six years.

Hybrid

Hybrid mattresses combine pressure-relieving foam with the bouncy, cooling coils of an innerspring mattress. The idea is to have the benefits of a foam and innerspring mattress while minimizing both of their drawbacks. To qualify as a hybrid, the mattress needs at least two inches of foam.

Hybrid mattresses can suffer from the drawbacks of an innerspring and foam mattress—the dense foam layer can still retain body heat, and the coils tend to sag within six to seven years. Quality hybrid mattresses are often one of the more expensive mattresses since they contain a high amount of materials.

Sleeping Positions

Your sleeping position can affect what mattress you should buy because each position is best suited to different firmness options. Your sleeping position isn’t just about feeling comfortable, as you need to make sure your spine remains neutral.

Side Sleeping

Side sleeping is the most common sleep position, with plenty of health benefits. You breathe better lying on your side, as the soft tissue at the back of your throat is less likely to block your airway. And sleeping on your right side reduces pressure on your heart.

Soft and medium mattresses for side sleepers are usually best, as they’re plush enough to cushion the shoulders and hips. However, you don’t want a mattress that’s so soft it causes your spine to bow, as this can lead to back pain.

SEE ALSO: What is a Plush Mattress? Who Is it Best For?

Back Sleeping

Back sleeping may be the best position for your spine, maintaining neutral alignment. However, if you’re a back sleeper, you’re more likely to experience symptoms of acid reflux, snoring, and sleep apnea. When you lie flat on your back, it’s easier for the soft tissue at the back of your throat to collapse, interrupting your breathing. Similarly, lying on your back means it’s easier for the contents of your stomach to flow up your esophagus.

If you snore or have sleep apnea, but can’t fall asleep unless you’re on your back, try an adjustable base or wedge pillow to elevate your upper body. Most back sleepers sleep best on a medium-firm to firm mattress, although some do find medium mattresses with added back support comfortable.

Stomach Sleeping

Stomach sleeping is the least common sleep position and not recommended since it can leave you waking up in pain. Sleeping on your stomach stretches your spine out of alignment when gravity pushes down on your stomach. You may also wake up with neck pain from twisting your neck at an awkward angle to breathe as you sleep.

If you can’t feel comfortable enough in another position to fall asleep, look for a mattress with a medium-firm to firm feel to prevent sinkage. As a further precaution, you can keep a pillow under your stomach and use a thin head pillow.

Combination Sleeping

Combination sleepers move between two or all three sleeping positions in the night. They can sleep comfortably on most mattresses, but the best mattress for a combination sleeper is one that suits their dominant sleeping position.

If you don’t know what your dominant position is, keep track of how you tend to wake up. If you’re still unsure what the best mattress firmness for you is, try a medium mattress for a balanced feel.

Mattress Firmness

The best firmness level for you will depend on your sleeping position, body type, and personal preferences.

Our sleeping position section details the best firmness for each position. Your body weight is another factor, as heavier sleepers need a firmer mattress to withstand their weight, while petite sleepers need a softer mattress to relieve pressure points. You qualify as a heavy sleeper if you weigh more than 230 pounds and as a petite sleeper if you weigh less than 130 pounds.

If you’re buying a mattress in a box online and want an idea of how it feels, read customer reviews. See what previous customers had to say about the mattress, particularly those who owned the mattress for three months or more.

Sleep Trials, Warranties, and Return Policies

Reading through an attached sleep trial, warranty, or return policy gives you an idea of the mattress’s quality. If the company includes a short warranty or only accepts returns under limited circumstances, it might lack confidence in its product’s quality.

Sleep Trial

Online mattress companies popularized sleep trials, which let you try out your new mattress in the comfort of your home. Most trial periods last 90 to 120 days and start once the mattress has been delivered.

If you are not happy with your mattress during the sleep trial, the company will often help you donate it and give you a full refund. The mattress company may ask that you wait a month before returning or exchanging your mattress, as you may need the time to adjust to your bed.

Warranties

If a mattress doesn’t include a warranty, we strongly recommend you do not purchase as you would be buying a mattress without protections. Warranties guarantee coverage for manufacturing and quality defects, such as sagging beyond a certain depth (usually an inch). You need a proof of purchase to make a warranty claim, so hang onto your receipt.

Read through the details of the warranty to see what’s covered and what can void your warranty—warranties are void if liquid spills onto the mattress or if the bed frame doesn’t offer enough support, leading to premature sagging. Protect your mattress against liquid damage by encasing it in a mattress protector.

Return Policies

If the return policy is not paired with a sleep trial, you typically have 30 days to return a mattress. As people often adjust to a mattress within a month, a 30-day return policy still gives you the chance to discover how well you sleep on a new bed. Don’t forget to read through the return policy to learn the conditions under which you can make a return.

Saving on a Full Size Mattress

Getting a highly affordable full size mattress can depend on where and when you buy. The best places to buy a mattress are often web-based stores that offer lower prices on their products, thanks to reduced overhead costs.

Meanwhile, the best times to buy a mattress include the following mattress sales:

• Best Presidents Day Mattress Sales
• Best Memorial Day Mattress Sales
• Best 4th of July Mattress Sales
• Best Labor Day Mattress Sales
• Best Columbus Day Mattress Sales
• Best Black Friday Mattress Sales
• Best Cyber Monday Mattress Sales

Other Things to Consider

What are the dimensions of a full size mattress?

A full size mattress measures 54 inches wide and 75 inches long. People who like to sprawl or often change positions may feel cramped on a smaller twin bed. The added width of a full size mattress can make it easier to fall asleep and wake up refreshed.

How much bigger is a full XL size mattress?

A full XL size mattress is 5 inches longer than a standard, similar to how a twin XL mattress is 5 inches longer than a twin. Full XL mattresses are great for taller sleepers, but they’re a nonstandard size that can be difficult to find. If you want a wide mattress that’s 80 inches long, a queen mattress is easier to find than a full XL.

What’s the best full size mattress for a side sleeper?

A full size mattress for a side sleeper should offer a soft, conforming surface. If the mattress is too firm and lets pressure build up in the body, a side sleeper will wake up stiff and sore. A good mattress for side sleeping provides a soft to medium feel.

Memory foam, latex, and hybrid mattresses are all excellent options for side sleepers. Traditional innerspring mattresses tend to establish a too-firm surface for side sleeping.

Is a full size mattress big enough for a couple?

A full mattress is not recommended for couples because each partner would have about 27 inches of space, which would be quite the narrow fit for many couples. We suggest a queen or king size bed for couples. Queen mattresses are more popular than king mattresses, as they are less expensive and fit in smaller bedrooms.

What’s the average cost of a full size mattress?

Most high-quality full size mattresses cost anywhere between $700 to $1,500. You may be able to find some in the $500 range, but we don’t suggest buying mattresses priced any lower than $500. When determining if your bed is a good value, compare its price to its features. If it seems like you’re paying a lot of money for a bed that’s rather basic, consider other options, instead.

Conclusion

Full size mattresses offer 16 more inches of sleeping space than a twin mattress, leaving a solo sleeper with plenty of room to sprawl. However, the bed size does not provide enough space for more than one person. If you want a bed large enough to share with someone else, look at a queen or king size mattress.