Power systems perfect balance and durable construction guaranteed to retain its’ shape. Durable, hollow, synthetic rubber with a textured surface that makes them easy to hold, toss, catch or bounce. Eleven weights available, from two to thirty lbs. Color coded by weight for easy identification. Kits and racks available. features & benefits: add interest and variety to workouts improve power and coordination enhance range of motion easy-grip design 11 different sizes and weights available 3-year limited warranty