Experience premium support and perfect sleep with our new Serta® Quilted Perfect Sleeper X™ collection. Our 5 ZoneResponse™ Design is comprised of Perfect Conform™ Memory Foam paired with 5-zoned coils for full-body alignment. Sleep comfortably cool throughout the night with cooling technology and graphite-infused memory foam designed to redistribute heat away from your body. A quilted top offers a classic feel and added layer of plush foam. Extraordinary sleep is possible, with Serta® Quilted Perfect Sleeper X™. The Knox Firm features 5 support zones designed for full-body spinal alignment with a combination of supportive coils and Perfect Conform™ Memory Foam. Plus, a classic quilted feel that makes for night after night of perfect sleep. Memory foam and cooling upgrades available. Firm and supportive; ideal for stomach or back sleepers. 5 ZoneResponse™ Design - combines coils and contouring memory foam full-body spinal alignment designed to offer comfort and support where you need it most. Perfect Conform™ Memory Foam - Premium, graphite-infused memory foam designed to provide targeted pressure relief and redistribute heat away from the body. Your new mattress may initially feel firmer than expected. Please allow up to 60 days to acclimate to your new mattress as it naturally adjusts to contour, comfort, and support you best.  100% USA Assembled, CertiPUR-US Certified. CertiPUR-US® certified means our foam was tested for and is free from harmful chemicals and gasses. Compatible with most frames, including: traditional frames, box springs, platform frames, slatted frames, bunky boards, and adjustable frames. Premium memory foam is temperature-sensitive; it may feel firmer in cooler temperatures and softer in warmer ones. For your preferred comfort, please allow several hours for your memory foam mattress to adjust to the room’s temperature.  Mattress Top Type: Tight Top Mattress Type: Hybrid Included: 1 Box Spring(s), 1 Mattress(es) Features: Full Support, Wrapped Coils, Cushioning Layer, Foam Layer, Cooling Layer Additional Information: Eliminates Motion Transfer, Conforms To Body, Relieves Pressure Points, Suitable for Adjustable Bed Frames Coil Count: 647 Coils Manufacturer Warranty: 10 Year Limited Bed Size: Twin Xl Measurements: 80 Length/Inches Maximum Weight Limit: 850 Lbs Base Material: 70% Polyurethane, 30% Metal Comfort Type: Firm Mattress + Box Spring Measurements: 38 Width/Inches, 80 Length/Inches, 23.25 Depth/Inches Care: Spot Clean Certifications And Listings: Certipur-Us Certified Mattress Height: 14.25" Country of Origin: Made in US Set includes mattress plus box spring/foundation. King and Cal. King mattress sets feature 2-piece side-by-side foundations for easier navigation in tight spaces.