Serta Northlight Plush Mattress Set, Twin XL The Serta perfect sleeper is the only official mattress of the national sleep foundation (NSF), designed to help address 5 common sleep problems Cool action gel memory foam: in perfect sleepers for the first time, this revolutionary foam delivers pressure relief while reducing heat build-up Custom support system: a durable, yet flexible all-foam support system is engineered to provide the right amount of support across the entire body Mattress Set includes Serta Perfect Sleeper Low Profile 6" Stable-Base Foundation