Our team at Sleep Foundation conducts extensive hands-on tests for each mattress to provide you with the most reliable, data-driven recommendations and reviews. Below are key guidelines that inform our testing methodology:
Our testers lie on the surface of each mattress to evaluate factors such as contouring and support. We also use specialized tools to measure performance criteria like pressure relief, heat retention, and motion isolation.
We test each mattress using various sleep positions to observe whether a mattress is better suited for side, back, or stomach sleeping. We roll around the surface and sit on the edges to gauge ease of movement and perimeter support.
We have tested hundreds of mattresses and bring years of experience in the mattress industry to the test lab. Our testing team covers a wide range of sleep preferences, sleep positions, and body types. This helps us represent as many sleeper types as possible in our reviews.
Firmness Options: Medium Soft (4), Medium (5), Medium Firm (6), Firm (8)
At a Glance
The CST Serenity is a dual-firmness latex mattress with a different feel on each side. This design allows you and your sleep partner to both rest easy if your firmness preferences differ.
Ratings Summary
Motion Isolation
6.5/10
Edge Support
7/10
Temperature Control
8/10
Ease of Movement
7.5/10
Off Gassing
8/10
Pressure Relief
7.5/10
Pros
Dual-firmness design has a different feel on each side
Responsive latex construction lets you move on the surface with ease
Excellent breathability and temperature control
Cons
Limited motion isolation for co-sleepers
Only available in three sizes
Above-average pricing even by latex mattress standards
Custom Sleep Technology is a Connecticut-based company that specializes in latex mattresses and sleep accessories. The company, which also brands itself as CST, offers three mattress models — the Essential, the Serenity, and the Performance — each of which comes in several customizable variations.
The Serenity is a split firmness mattress sold in queen, king, and California king sizes. This means you can choose different firmness levels for each side of the mattress, making this bed a great choice for couples who have a hard time compromising on their comfort preferences. Unlike a traditional split mattress setup, which places two smaller mattresses side by side, the Serenity’s dual firmnesses are incorporated into a single mattress.
Our review focuses on the Serenity Blended Dual-Density Talalay Latex Mattress — also known as simply the Serenity Blended Mattress — which contains both natural and synthetic latex. The company also offers the Serenity in 100% natural Talalay latex at a higher price-point.
The Serenity Blended Mattress has four firmness options for each side of the bed, meaning there are 12 possible configurations (you can’t select the same firmness for both sides).
Custom Sleep Technology calls its firmness options Soft, Medium, Firm, and Extra Firm. However, our testing team determined that these correspond to medium soft (4), medium (5), medium firm (6), and firm (8) on our 10-point firmness scale. To avoid confusion, we’ll use CST’s terminology throughout this review.
Our testers evaluated a version of the bed with a Left Soft/Right Firm configuration because it’s the most versatile combination that satisfies the needs of the widest range of sleepers. We’ll share the results of our sleep lab tests and provide a complete breakdown of the mattress’ materials and construction. We’ll also go over the company’s policies, including shipping details and warranty terms.
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Sleeping Style and Body Weight
Custom Sleep Technology Serenity Dual-Density Latex Mattress – Left Side
Sleeper Type
Under 130 lbs
130-230 lbs
Above 230 lbs
Side Sleepers
8/10
6.5/10
5/10
Back Sleepers
8/10
6.5/10
5/10
Stomach Sleepers
6.5/10
5/10
5/10
Custom Sleep Technology Serenity Dual-Density Latex Mattress – Right Side
Sleeper Type
Under 130 lbs
130-230 lbs
Above 230 lbs
Side Sleepers
6.5/10
8/10
8/10
Back Sleepers
8/10
6.5/10
6.5/10
Stomach Sleepers
8/10
6.5/10
5/10
Side Sleepers
Our testers noticed a distinct difference in feel between the two sides of the bed. The Soft side offered more contouring that worked well for our side sleepers who weigh under 130 pounds. The Firm side offered better support for testers over 130 pounds, who noted that they sank just enough into the top latex layer to receive pressure relief without uncomfortable sinkage.
Back Sleepers
The Soft side comfortably hugged the hips while supporting the lower back for our back sleepers under 230 pounds. The Firm side provided adequate support for testers over 230 pounds, but back sleepers in this weight category may prefer the Extra Firm version of the Serenity Blended Mattress for greater back support.
Stomach Sleepers
The stomach sleepers on our testing team preferred the Firm version’s latex formulation regardless of body type. While those under 130 pounds felt reasonably comfortable on the Soft option, even these testers liked the more balanced feel of the Firm version. Like our back sleepers over 230 pounds, stomach sleepers in that weight group said the Extra Firm option is a better fit for their sleep preferences.
Mattress Performance
In addition to the hands-on feedback from our team, we conduct a number of quantitative tests in our Test Lab. The below ratings are based on the experience of our testers.
Motion Isolation
6.5
/ 10
Medium Soft: 8 / 10
Medium: 7 / 10
Firm/Extra Firm: 6 / 10
Unlike many foam formulations, latex mattresses tend to have more responsiveness. The Serenity Blended Mattress is even bouncier than most latex mattresses we’ve tested, meaning light sleepers may feel vibrations if their sleep partner is an active sleeper.
Pressure Relief
7.5
/ 10
Medium Soft: 8 / 10
Medium: 7 / 10
Firm/Extra Firm: 6 / 10
Pressure relief refers to how well a mattress contours to the shape of your body, evenly distributes your weight, and prevents pressure points from forming at key contact areas like the hips and shoulders.
The blended latex layers of the Serenity Blended Mattress are moderately contouring and offer a modest amount of pressure relief on both the Soft and Firm sides of the bed.
Temperature Control
8
/ 10
Medium Soft: 6 / 10
Medium: 7 / 10
Firm/Extra Firm: 8 / 10
Latex tends to be one of the more breathable mattress materials because it’s less contouring than many foam formulations and does not hug the body as closely, allowing for better air circulation.
During our tests, the latex layers of the Serenity Blended Mattress remained noticeably cool. Our testers attributed it to the use of Talalay latex, which has an airier formulation compared with denser latex made through the Dunlop method.
Edge Support
7
/ 10
Medium Soft: 5 / 10
Medium: 6 / 10
Firm/Extra Firm: 8 / 10
The latex construction of the Custom Sleep Technology Serenity Blended Mattress provides adequate edge support but sags slightly when sitting or lying at the outermost edges of the bed.
We tested the Left Soft/Right Firm version, which we determined were medium soft (4) and medium firm (6) on our firmness scale. Interestingly, despite the overall firmness differences, we found that the two sides did not have a major difference in edge support.
Ease of Movement
7.5
/ 10
Medium Soft/Medium: 7 / 10
Firm/Extra Firm: 9 / 10
This model contains three layers of blended latex that provide a buoyant, springy surface which regains its shape quickly as pressure is lifted. This ease of movement is especially helpful for active sleepers and people with reduced mobility.
It’s important to note that a person’s body weight can influence this metric. People who weigh over 230 pounds may find that they sink slightly deeper into the bed’s top layer.
Off-Gassing
8
/ 10
Off-gassing describes the chemical smell that results when you unbox a mattress containing synthetic foam. Since natural latex is made from the sap of rubber trees, it doesn’t off-gas in the traditional sense. However, synthetic latex is made from petrochemicals, so it generally emits a faint odor after being unwrapped.
The Custom Sleep Technology Serenity Blended Mattress contains a mix of natural and synthetic latex, so our testers noticed a slightly greater degree of off-gassing than a typical latex model. That said, the odor dissipated quickly and didn’t approach the off-gassing levels of some memory foam mattresses we’ve tested.
The Custom Sleep Technology Serenity Blended Dual-Density Latex Mattress features three layers of blended latex, a formulation that combines natural Talalay latex with synthetic latex. The company lets you choose two different firmness levels, one for each side of the bed.
The comfort system contains two 3-inch latex layers. The density of the latex formulation varies depending on which firmness level you choose. While Custom Sleep Technology calls the firmness options Soft, Medium, Firm, and Extra Firm, our testing team determined that these correspond to medium soft (4), medium (5), medium firm (6), and firm (8) on our 10-point firmness scale.
Three inches of dense latex form the sturdy support core. Each of the latex layers is wrapped in an organic cotton liner for protection.
Firmness
Medium Soft – 4, Medium – 5, Medium Firm – 6, Firm – 8
Mattress Type
Latex
Construction
Cover Material:
Tencel or Organic Cotton
Comfort Layer:
3″ Blended Latex
3″ Blended Latex
Support Core:
3″ Blended Latex
Custom Sleep Technology Serenity Mattress Sizes
The Serenity’s unique dual-firmness design may make it a worthwhile investment for some shoppers — particularly couples with markedly different comfort preferences. This model is only available in queen, king, and California king sizes.
Sizes
Dimensions
Height
Weight
Queen
60″ x 80″
9″
N/A
King
76″ x 80″
9″
N/A
California King
72″ x 84″
9″
N/A
Trial, Warranty, and Shipping Policies
Availability
The Custom Sleep Technology Serenity Blended Mattress is available exclusively through the company’s website.
Shipping
The mattress ships for free within the contiguous U.S. and for a fee to Alaska and Hawaii. The bed’s three layers are vacuum-sealed and packaged separately to make it easier to move and unpack in your bedroom.
The company uses UPS Ground shipping services. Delivery typically takes about three weeks from the time you place your order.
Additional Services
Custom Sleep Technology offers in-home mattress setup for customers in Connecticut, New York, New Jersey, Massachusetts, and Rhode Island. The company does not include old mattress removal as part of this service.
Sleep Trial
CST does not offer a sleep trial with any of its mattresses.
Warranty
The Custom Sleep Technology Serenity Blended Mattress is covered by a 10-year limited warranty. The warranty protects against manufacturing defects, including flaws in the workmanship or materials. If a mattress is deemed defective, the company either refunds the purchase price or repairs or replaces the bed at its discretion.
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