The Caldwell Hydrosled provides shooters with the most advanced recoil reducing shooting rest on the market and the versatility to fit virtually any shotgun or rifle, all built around a highly portable shooting platform. A key feature of the Hydrosled is the ability to fill the reservoir with any kind of media (rocks, sand, water, etc.) while shooting and empty the reservoir when it is time to transport or store. With many adjustments to align and secure the gun perfectly and the non-marring contact points, this rest will make sighting in your weapon comfortable and reliable. Mfg: Caldwell Shooting Supplies