The Classic Plyo Boxes provide maximum stability and durability with their steel construction and fully welded frames. Any athlete can use these boxes for forward jumps, lateral jumps, or other plyometric drills. Tops are reinforced 3/4-inch plywood with a non-slip surface to maximize safety. Rubber bottoms protect floor surface and prevent sliding. Legs are constructed at a 6-degree angle to prevent tipping. Use both indoors and outdoors. Stackable for easy storage. 4 Box Set: 12, 18, 24 and 30-inch boxes 5 Box Set: 12, 18, 24, 30 and 36-inch boxes 6 Box Set: 12, 18, 24, 30, 36 and 42-inch boxes.