FEATURES: Improve pitching mechanics through overload and underload training Build arm strength and promote blood flow and active recovery Includes five weighted plyometric balls for versatile training Pliable material allows you to see impact Come with custom drills for each weight option ADDITIONAL DETAILS: Weight options include 3.5oz., 5.25oz., 10oz., 15oz. in a 9" circumference and 20oz. in a 12" circumference