Frontal view of the South Bay Sofinity Hybrid Signature 12-inch firm mattress featuring navy blue piping on a contemporary rattan platform bed.

Close-up detail of the Sofinity foam mattress quilted top with premium navy blue edge piping and breathable side fabric.

High-angle bedroom shot of the Sofinity Hybrid Signature firm mattress showcasing the wide sleep surface on a natural wood bed frame.

Isolated studio shot of the South Bay Sofinity Hybrid Signature 12-inch mattress showcasing the white tufted surface and dark grey borders.

Minimalist frontal studio view of the 12-inch thick Sofinity Hybrid Signature firm mattress against a clean white background.

Top-down studio perspective of the Sofinity Hybrid Signature mattress highlighting the tufted quilted cooling cover.

Infographic explaining Patented Edge to Edge technology for the South Bay mattress, providing a stable sitting edge and 20% more sleeping surface.

Diagram of Individually wrapped steel pocketed coils for the Sofinity Hybrid mattress, promoting motion isolation and increased airflow.

Cooling feature graphic for Sofinity Hybrid mattress highlighting 3x cooling technology with a Tencel cover and breathable pocketed coils.

Mattress firmness scale for Sofinity Hybrid Signature indicating a medium-firm feel, ideal for stomach, back, and side sleepers.

Detailed construction diagram of the 12-inch Sofinity Hybrid mattress featuring a cooling Tencel cover, Sofinity foam, and expanded edge stability.

Sofinity Hybrid Signature, Sofinity Foam, Patented Edge Support - Firm 12 inch Mattress By South Bay

Plush Medium Firm Pillow top Memory foam Hybrid

Sofinity Hybrid Signature, Sofinity Foam, Patented Edge Support - Firm 12 inch Mattress By South Bay

$788.00

$999.00

Save $211.00

Brand:

SOUTH BAY

i Size Guide

$788.00

Only 12 left in stock

Free USA Wide Delivery

10 Year Warranty

Advanced Technology

The Sofinity Hybrid Signature Mattress brings together advanced Sofinity Foam technology and responsive pocketed coil support in a premium firm-feel 12-inch hybrid build.

Cloudy Mattress is the authorized South Bay retailer for this product, so every purchase comes with trusted sourcing and the full manufacturer's warranty.

The feel sits on the firm side of the comfort scale, making it an ideal 12-inch firm hybrid mattress for back and stomach sleepers seeking structured support. Because of this stable, no-sink response, it ranks among the best 12-inch firm mattresses for back pain options for those who want both pressure relief and lift.

Inside, multiple engineered layers work together, starting with Sofinity Foam at the surface for ergonomic body contouring with twice the airflow of traditional foam. This proprietary foam delivers a lightweight, breathable feel that conforms to the body while promoting spinal alignment and support foam performance.

Furthermore, the gel-infused cooling memory foam layer pulls heat away from the body, supporting a temperature-neutral sleep surface throughout the night. This cooling firm hybrid mattress king and queen design suits hot sleepers who still want the structured support of a firm hybrid.

The mattress also features individually wrapped pocketed coils that deliver responsive lift with superior motion isolation for couples sharing the bed. A M-Guard patented edge support system reinforces the perimeter, adding roughly 20% more usable sleeping space with M-Guard edge reinforcement for stability.

Together with Sofinity reactive high-density foam, these layers deliver targeted lumbar back support and durable no-sag mattress construction night after night. The Air Channel™ base foam promotes airflow through the core, enhancing breathability and adding flexibility for use with adjustable base compatible mattress setups.

At a full 12-inch profile, this firm hybrid mattress with M-Guard edge support is fully adjustable-base compatible and pairs seamlessly with modern foundations. Together, these layers deliver a hotel-quality luxury firm feel that combines responsive coil support with advanced Sofinity Foam comfort for restorative deep sleep support.

Sofinity Foam Technology

Proprietary Sofinity Foam delivers ergonomic body contouring with twice the airflow of traditional memory foam for a cooler, more breathable sleep.

Firm, Supportive Feel

This 12-inch firm hybrid mattress delivers structured pushback ideal for back and stomach sleepers seeking targeted lumbar back support.

Cooling Gel Comfort

Gel-infused cooling memory foam dissipates body heat for a more breathable sleep surface, especially valuable for hot sleepers.

Pocketed Coil Hybrid Support

Individually wrapped pocketed coils deliver responsive support with superior motion isolation for couples sharing the bed.

Patented Edge Support

The M-Guard patented edge support system reinforces the perimeter, adding roughly 20% more usable sleeping space.

Durable, No-Sag Build

Sofinity reactive high-density foam combined with the coil core delivers durable no-sag mattress construction for years of consistent comfort.

Certified Clean Foams

All foams are CertiPUR-US certified foam and non-toxic certified sleep materials, made without formaldehyde, phthalates, heavy metals, or ozone depleters.

Key Mattress Benefits

7 Layers
Of Cooling
Comfort

This top layer is South Bay's proprietary Sofinity Foam, engineered with roughly twice the airflow of traditional foam for enhanced temperature regulation. The lightweight, open-cell structure contours effortlessly to the body while promoting healthy spinal alignment.

This layer is the gel-infused cooling memory foam that adds plush contouring and dissipates body heat. As a result, sleepers benefit from cradled comfort at the shoulders and hips with a cooler surface feel.

A reinforced perimeter is built into the mattress to extend the usable sleeping area by roughly 20%. This system also provides a stable sitting edge when getting in and out of bed.

This core layer is built from individually wrapped pocketed coils that deliver responsive support and gentle bounce. Furthermore, the pocketed design reduces motion transfer between partners while promoting airflow through the core.

This bottom layer reinforces the structural integrity of the mattress with integrated channels that promote airflow. It anchors the entire build, supports long-term durability, and helps maintain a consistent shape over time.

The exterior cover unzips for easy laundering and helps reduce allergens with regular washing. Its breathable design complements the Sofinity Foam and gel cooling system at the surface of the mattress.

DISCOVER WHY BUYING WITH

CLOUDY MATTRESS IS THE SMARTER CHOICE

From better sleep support to trusted quality, Cloudy Mattress gives you more value for your money.

FASTEST SHIPPING

Get your new mattress delivered quicker than ever with our priority nationwide shipping.

24 / 7 CUSTOMER SUPPORT

Get your new mattress delivered quicker than ever with our priority nationwide shipping.

EXPERT GUIDANCE

Get your new mattress delivered quicker than ever with our priority nationwide shipping.

BEST PRICE GUARANTEED

Get your new mattress delivered quicker than ever with our priority nationwide shipping.

Hybrid done right - coils and foam working together

I've tried pure foam and pure coil mattresses. The Sofinity Hybrid is the best of both. The coils give responsive support and the Sofinity foam layer adds pressure relief on top. The result is a firm mattress that doesn't feel punishing. My back is supported and my pressure points are relieved. South Bay got the hybrid formula right.

Edge support is the best I've experienced

The patented edge support on this mattress is exceptional. I can sit on the very edge to put on shoes and it barely compresses. I can sleep right at the edge and the support is identical to the center. For a king-size mattress this extends the usable sleeping surface meaningfully. South Bay engineered this feature seriously.

Firm is very firm - know what you're getting into

The mattress quality is excellent and the edge support is genuinely impressive. My note is that this runs on the firm end of firm. I came from a medium mattress and the first two weeks were an adjustment. By week three I was comfortable and now I love it. If you're a dedicated firm sleeper you'll feel at home immediately. If you're transitioning give it time.

Firm without being hard - the difference matters

A lot of firm mattresses are just hard. Hard and firm are not the same thing. The Sofinity Hybrid is genuinely firm - supportive and pushback - but the foam layer means it doesn't feel like sleeping on a board. My lower back has never been better supported and I wake up without stiffness for the first time in years.

Hybrid gives better airflow than pure foam

I switched from a pure memory foam mattress because it slept hot. The coil system in the Sofinity Hybrid allows airflow that foam alone can't provide. Combined with the Sofinity foam comfort layer I get pressure relief without heat retention. Sleeping noticeably cooler and just as comfortable. A real advantage of the hybrid design.

HAVE QUESTIONS?

WE'VE GOT ANSWERS

Designed for deep comfort and better rest, so you wake up refreshed and ready for the day

The Sofinity Hybrid Signature combines Sofinity Foam's ergonomic contouring with a responsive pocketed coil core that promotes spinal alignment. Many sleepers find this combination helpful for general back comfort, especially in a firmer feel.

Both mattresses use Sofinity's hybrid construction principles with cooling foam and a pocketed coil core. The Signature line generally represents South Bay's premium tier within the Sofinity family, with refined comfort layers and a firmer feel suited to those who want structured support. The Essentials line offers similar core technologies at a more accessible value tier.

A box spring is not required. The mattress can be placed on a continuously solid surface, an adjustable base, or slats spaced no more than two inches apart. Cloudy Mattress also offers an optional box spring with a metal foundation as an add-on at checkout.

Yes, all foam layers in this mattress are CertiPUR-US certified. They are made without formaldehyde, phthalates, ozone depleters, heavy metals, PBDEs, or listed Tris flame retardants, and they meet low-VOC standards for healthier indoor air quality.

The M-Guard patented edge support system reinforces the perimeter of the mattress with denser foam framing around the coil unit. This expands the usable sleeping surface by roughly 20%, provides a steadier sitting edge when getting in and out of bed, and helps extend the mattress's overall longevity by reducing edge wear.

Still

Have Questions ?

Our sleep specialists are dedicated to helping you find the mattress of your dreams. Give us a call or chat with us now.

GIVE US A CALL

Speak directly with an expert to find the right support for your sleep style.

+1 800 540 9851

CHAT WITH US

Get the answers you need without picking up the phone.

Let’s Chat!

SEND US A MAIL

Prefer to write it out? Drop us a message, and we’ll get back to you within 24 hours.

Send An Email