The Hyper Wear SandBell is a cross between a sandbag, dumbbell, grip bag, medicine ball, slam ball and kettlebell. This ball can be slammed, thrown, tossed, or rebounded and is safe for partner work. The shifting of the sand challenges you, stabilizing the muscles. A SandBell will also increase grip strength when tossed or received. With a thick Neoprene shell, this ball is soft, stretchy and durable. The SandBell arrives empty and you fill it at your own pace, so you can work up to heavier weights on your own terms. Maximum weight for the SandBell can reach 50 lbs. To fill the SandBell use Dry Washed sand.