XM FITNESS Soft Impact Plyo Boxes are made from high-density foam and covered with 18oz.vinyl. The bottoms and tops are 30 oz. non-skid vinyl. Each box has a handle for easy repositioning and Velcro strips for stability when stacking. Stack any combination together for desired height. All boxes are 30" X 36". Heights that can be configured : 6" , 12" , 18", 24", 30" and 36"