Tested 21 Series Pump; Bi-Rotational; Single Unit; Sae 4 Bolt B Sec; 1”-15 Spline Shaft; With O.B Bearing; 1-1/2 Gear Width; Gear Housing: Blank Inlet Port,Blank Outlet Port;Port End Cover : Orb #16 Rear Inlet Port, Orb #16 Rear Outlet Port, Standard Studs.