Slumber 1 Mattress-in-a-box Size, Twin 8" Tight top bed mattress with individual spring coils Revolutionary rebound technology lets the mattress-in-a-box expand in minutes when unpacked Increased motion separation: springs provide undistributed rest Slumber 1 spring mattress is constructed to adjust individually to your weight and body shape Heavier gauge steel coil for durability and comfort with the Slumber 1 Mattress-in-a-Box