Popular 2" gasket for use with pump and heater unions that take a gasket with a 2-1/2" o-ring lip. Will fit unions by Waterway, Balboa, ACC HydroQuip and many more. These gaskets can come in clear, white and black but are all the same.If you're not sure which size you have please see our gasket combo kit which includes a pair of these gaskets and the other common size with a 2-5/8" lip here