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Firm
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On Sale
Mancini's Sleepworld Onyx Firm Mattress 13"-Split Cal King
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In Stock
Mancini's Sleepworld Onyx Firm Mattress 13"
Why this Mattress?
- Built to keep back sleepers cool, lifted, and properly supported all night long
- Gel-infused memory foam pulls heat away from the surface
- Fabric-wrapped pocketed coils move independently to reduce motion transfer
- High-density firm comfort layers resist sagging year after year
- Heavyweight cold-touch knit cover works from the first night
Overview
Mancini's Sleepworld Onyx Firm Mattress 13" Split Cal King
The Mancini's Sleepworld Onyx Firm Mattress 13" is a firm innerspring mattress built for the back sleeper who runs warm and wakes up stiff. At 13 inches tall, it layers gel memory foam and high-density support foams over a pocketed coil system engineered to hold the lumbar in place without pushing back hard against hips and shoulders. The result is a mattress that feels planted and stable from edge to edge. If you want to feel the difference against every competing option at this price point, stop by any Mancini's Sleepworld location and our sleep specialists will line it up side by side so you can decide with confidence.
COMFORT AND FEEL: Firm innerspring feel with gel-infused memory foam cushioning and steady lumbar lift throughout the night.
SIZE: This Split Cal King sized mattress is 36" x 84" per side, ideal for couples who share a California King but prefer independent comfort zones.
BEST SLEEP MATCH: Best for back sleepers and select side sleepers who want a firm mattress for back pain relief. The firm coil system holds the spine flat while gel memory foam softens the contact points just enough to avoid pressure buildup.
BEST FOR: Ideal for sleepers who run warm, need consistent lumbar support, or have been waking up with tension across the lower back.
CONSTRUCTION SPECIFICATIONS: The heavyweight cold-stretch knit cover draws surface heat away immediately. Gel-infused memory foam in the quilt layer adds cushioning without trapping warmth. A 1" med-firm high-density comfort layer transitions smoothly into 1.5" of extra firm high-density support foam. The fabric-wrapped pocketed coil system moves independently so one partner's movement stays on their side. A shock-absorbing high-density base foam anchors the whole stack. Foams are CertiPUR-US® certified.
SETUP AND COMPATIBILITY: Delivered flat with in-home professional setup available. Compatible with adjustable bases, platform frames, and standard box springs. No tools needed for setup.
NOT A FIT FOR: Not ideal for side sleepers who need deep pressure relief at the shoulder, or for anyone who prefers a plush or pillow-top feel.
YOUR SLEEP, BACKED BY US
Every mattress purchase at Mancini's Sleepworld comes with a 120-night comfort guarantee and our Rest Easy Promise. Come try this one in any of our showrooms before you buy. We include free next-day delivery, in-home professional setup, and flexible financing. Add a premium mattress protector at the time of purchase and you can choose to extend your guarantee to a full 365 nights. We also back every purchase with our Best Price Guarantee.
- SleepMatch: blue
Rest Easy Promise
Our promise to you.
- 365-Night Comfort Guarantee with purchase of a premium mattress protector
- Best Price Guarantee Find it lower and we’ll match it.
- Free Next-Day Delivery We’ll deliver to your door, set-up available.
- Double-Your-Warranty We match the manufacturer’s warranty.
Features
- SKU: BRK-ONY-6SM-FM-25
- MPN: 25WICRAFF_FP36X84
- GTIN: 810146419174
- Brand: Mancini's
- Collection: Sleepworld
- Type: Innerspring
- Mattress In A Box: No
- Firmness: Firm
- Height: 13
- Length: 84
- Width: 36
- Shipping Height: 13
- Shipping Width: 84
- Shipping Length: 36
- Warranty: 10 Year
- Cover Material: Polyester Knit
- Quilting Layers: 3/4 H.D Gel Infused M - Foam, 3/4 Extra Firm Quilt Poly
- Comfort Layers: 1'' Med-Firm H.D. Foam,1.5'' Extra Firm H.D. Support Foam
- Support System: 8'' 840 Pocketed coil ,1.0'' Shock Absorbing H.D. Base Foam
Specification
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Suitable For Adjustable Base: Yes
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Motion Separation: Yes
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Cooling Technology: Yes
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Edge Support: Yes