BACK IN STOCK! The Onnit HydroCore Bag

When you lift the HydroCore bag, it wants to keep going in whatever direction you were moving it. The water inside it sloshes around, and your shoulders, hands, hips, and core have to work to stop it from pulling you out of position and breaking form.

Overcoming all that inertia builds head-to-toe stability—the kind you need to hold onto a resisting opponent if you’re a fighter, lift heavier weights if you’re a gym rat, and prevent injury if you have a history of low-back pain.