The SMAI Commercial grade medicine ball is a high grade quality ball with superior internal construction, designed to outlast the competition. Triple layer construction starts with a tough inner bladder, followed with a thick nylon wall for weight & strength, and finally a durable rubber outer shell. Product note: warranty does not cover the use of medicine balls when used as a slam ball. Meaning the balls are not to be thrown to the floor repetitively. If you intend to use the balls for throw a