If you boat in freighter, large yacht, or swimmer traffic, it’s important to protect from boats, people, and docking surfaces. The BISupply Bumper Dock Fenders 2pk prevents wake damage and is used for crabbing or trout line end markers, navigating, mooring, water safety. Needed size depends on dock surface, hull shape (distance from hull to dock at waterline), and water conditions, but our marine buoy ball float fits most and even works on winter ice. They come deflated for shipping, but we provide a free air pump. To avoid damage, do not overflate. Deflate after use by inserting inflator pin needle without air pump. The boat fenders bumpers are intended to be filled with air to float, but you can add air and then water to use as a water bag punching bag (water pump needle not included). Warning: This product can expose you to chemicals which is [are] known to the State of California to cause cancer and birth defects or other reproductive harm.