Impeller F9 - 9 Blade - Neoprene Pump:F9 Material:Neoprene (for cooling) Outer Diameter:3.74' Inner Diameter:Splines Width:3.48' 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.