Impeller Pump:F4 Material:Nitrile (oil resistant) Outer Diameter:2.0' Inner Diameter:0.47' Width:0.87' A worn or damaged impeller can cause system failure or engine breakdown. SPX's 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.