The SURGE Hydro Ball - HB25 is workout tool that uses water as its source of weight. As such, the water provides instability, which targets and activates more muscles than traditional weights. It’s a great training tool that allows for the weight to be adjusted up to 25 lbs. based on user’s workout needs. Water moving within the HB25 challenges the core, stabilizer muscles, and postural muscle groups more than traditional static weights. It was designed to be dropped, tossed, and slammed so it can be used like a Kettlebell, Slam Ball, or Medicine Ball. Consider it as an addition to the home or commercial gym. It retails on-line for over $65, bargain here. It is available for local pick-up in San Rafael, cash, Venmo, or PayPal.