The Geigerrig Power Bulb Holder firmly wraps the Power Bulb from your Geigerrig engine to keep it in place on any pack strap. The bulb holder uses heavy duty velcro three-wing encolsure to stay secure and can be easily repositioned for comfort and fit. The bulb holder comes strongly recommended for anyone who owns a Geigerrig hydration engine but uses it in a non-Geigerrig pack.