This Interpump RS500 gearbox will fit the following Interpump pump models and more:
E3B1515 E3B2121 E3B2515 W1550 W2030 W2035 W2141 W2525 W3018 W3021 W3025 W3521 W3523 W4015 W4018 W4518 W5015 W5018 WS151 WS201 WS202 WS251
For the engine, this gearbox will fit Honda engines up to 25HP that have a 1" shaft (GX240, GX270, GX340, GX390, iGX390, GX630, GX690, iGX700, iGX800 etc) and many other brands.
Please contact us if you are unsure whether this will suit your application.