These Hotsy Duplex Piston Pumps may be a bit smaller than the customary pressure washer pump, but they aren't small in performance! These two piston Hotsy pumps produce 1500 PSI Max pressure at 2.2 GPM with a 5/8" hollow shaft at 1725 RPM. These duplex pumps are primarily used on smaller, Hotsy electric pressure washer models 555ss, 558 and 559.