The under structure of this equipment is comprised of the finest 0.75" oak, covered in a dense foam which is upholstered in tough 38 oz vinyl. Each corner is strengthened with two stainless steel brackets. A raised lip on all boxes allows for stacking and locking of the lids. The 24 box is bottomed with 0.75" high density rubber for stability. With four primary pads and four curved corner pads there are no sharp edges or dangerous corners exposed to the athlete. Stainless steel handles are recessed on two sides of each box. Each pad is individually replaceable.