Steel Interior Frame With Wood Slats and a Knitted Polyester Cover A MATTRESS GAME-CHANGER - Any decent mattress needs a good foundation behind it, and this box spring is one of our best; built with all of the trusted support we put into our ever-so-popular platform beds, this game-changing box spring has the total package - an unwavering steel structure, reliable, closely spaced wood slats and a compact, cleverly developed, well, package DURABLY ENGINEERED - Durable steel and wood slats are used to construct the interior framework of this foundation; twin size supports a maximum weight capacity of 350 lbs, while all other sizes can support up to 700 lbs THOUGHTFULLY PACKAGED - All parts, tools and instructions are packed into one compact box that ships straight to your door Box spring only, a bed frame or platform bed is required to support this foundation and is sold separately Worry-free 5 year limited warranty included; box spring only, a bed frame or platform bed is required to support this foundation and is sold separately