Perfect for upper extremity exercise, the varying degrees of resistance and elasticity is ideal for hand, wrist and forearm programs. Constructed of high quality rubber, special agents are added for durability and strength. Includes a user's manual with 39 illustrated exercises. Available in three resistance levels: Light (yellow), Medium (Red), Heavy (Green). 7" (18cm) in diameter and weights eight ounces. It's a No Brainer... Increasing your hand, forearm and wrist strength... Increases your Power at the Plate!!