Plyometrics are great cardio and help improve your speed and agility. These platforms are nice because they stack for easy storage when you"re not using them. Use them inside or out. The anti-skid rubber top makes sure you don"t slip off the platform. * Plyometric platforms have become one of the most important training devices in gyms today. Great for improving explosiveness, speed and vertical jump. Proper plyometric training will help minimize muscle strain and injury. Platforms are constructed of 1 in. diameter 16 gauge steel tubing with powder coated finish and a 3/4 in. plywood top covered with heavy non skid rubber. For indoor or outdoor use. Stackable design for easy storage. Top measures 20 in. x 20 in.