Kings Brand Furniture Box Spring Foundation for Full Size Mattress with Legs, NO Bed Frame Is Required Box Spring Foundation for Full Size Mattress with Legs, NO Bed Frame Is Required . Quick assembly, 100% polyester Cover included. Comes KD for shipping purposes, will fit up narrow hallways/stairwells. This mattress foundation is built extra strong for heavy mattresses. Dimension: 75" x 54" x 12" from the floor to the top of the box spring when the legs are attached.