Sturdy Steel Frame With Poly Jacquard Cover AS SIMPLE AS UNFOLD & UNWIND - Requiring no tools and zero tedious assembly, the innovative No Assembly box spring requires only unfolding to become bedtime ready; the hardest part will be taking it out of the box DURABLY ENGINEERED - Durable steel is used to construct the interior framework of this reliable foundation; twin size supports a maximum weight capacity of 350 lbs, while all other sizes can support up to 700 lbs; King size is a split version