Center placed sand chamber for excellent balance and rotation Textured panels ensure a secure grip for safety and stability while exercising 9 and 12 lb models Features PowerCore and EverGrip technologies Enhance your training with medicine ball routines. The textured surface featured on this Powercore model helps ensure grip during passing and throwing routines as well as bypassing the problem of sweaty hands. The Powercore center features a well balanced sand chamber that keeps the weight of the ball evenly distributed as well as allowing for excellent rotation.