68012 Mechanical Expansion Plug, Thumb Nut, Nominal Size (In.) 5/16, Min. Dia. (In.) 0.297, Max. Dia. (In.) 0.3375, Max. Back Air Pressure (PSI) 10, Max. Back Pressure (Ft. of Head) 24, Material of Construction Aluminum, Stainless Steel, Neoprene Rubber, For Use In Low Pressure seal in circular openings