Lightweight, strong, sturdy and durable boxes. Constructed of 1-1/4” welded square steel tubing. Non-marking glides on all 4-legs. Non-slip urethane coated surface supplies cushion and protection as it wraps over the edge of the box. Strong enough to hold the BIGGEST athlete. Top dimensions range from 35.5” x 35.5” x 36” to 18” x 18” x 6”. Wheel kit assembly is available for box sizes 36” to 24”, easily attaches to the legs to make moving of boxes fast and easy! One side of all boxes is completely open so that all boxes slide into each other for compact storage, and easy transfer to work-out area.