The 2-in-1 Plyo Box (20 inch and 24 inch) offers two sizes for the price of one box. Two piece construction with a 20 inch Plyo Box on top and a 4 inch riser on the bottom easily convert the 20 inch box into a 24 inch box. Boxes with or without the riser are extremely sturdy and is made from 3/4 inch plywood. Exterior of box is sanded completely to avoid any sharp edges. Each box is sprayed with two coats of poly to protect the exterior wood. Ships fully assembled.