Conform to wide and out-of-round pipes with these inflatable plugs. Also known as pneumatic plugs, they're designed for temporary seals since they can lose pressure over time. Use the bypass tube on these plugs to add air, water, and other fluid to your pipeline or to relieve pressure while testing. Inflate with a hand pump (sold separately); an air compressor may overinflate the plug and cause damage. Tether the plugs using either the eyebolt or chain/ring so they don't get lost or stuck in your pipes. Maximum air back pressure is the amount of pressure a plug can withstand without moving. Maximum water back pressure refers to the pressure resulting from the height of the water above the plug.