Built with five different weight options, the Throwing Plyo Balls help improve pitching mechanics and arm strength. The various ball weights range from 3.5 ounces to 20 ounces, for overload and underload training. Use the lighter weights to develop the muscle memory needed between the brain and the body to develop fast twitch muscles. Train with the heavier weights to increase overall velocity and stamina. The set is designed for versatile training to assist with warm up, building strength, and active recovery. Includes custom drills for each weight to help build a training program that is right for you. Through consistent practice, athletes will develop the arm strength needed to make game-day plays. Designed with durable materials to last through seasons of use, the Throwing Plyo Balls come in two sizes, 9” circumference for weights 3.5oz., 5.25oz., 10oz., and 15oz., and 12” circumference for 20oz.