Engineered to surpass expectations, the Simpson 4.0GPM@4200 PSI AAA Professional Triplex Pump (90034) is highly efficient and minimizes engine load while delivering top performance. This easy-to-install pump replacement kit is for gas pressure washers* with a horizontal engine and a 1" diameter shaft. This pump can produce up to 4400 PSI at 4.0 GPM. The 90034 is designed with dual oversized ball bearings to reduce friction and allow for long lasting performance in the toughest cleaning environments. The 90034 features a stainless steel integrated unloader featuring our easy-start system. Check your pressure washer's inlet and outlet orientation to ensure compatibility.