ImpellerPump:F3BMaterial:Nitrile (oil resistant)Outer Diameter:1.78"Inner Diameter:0.31"/FlatWidth:0.50"A worn or damaged impeller can cause system failure or engine breakdown. SPXs Johnson Pump brand impellers are developed and manufactured for maximum flow and long life. With a genuine spare impeller you can also be sure that you are getting the quality required by engine manufacturers and professionals.