Interstate Pneumatics PW7172 Rear Inlet Pressure Washer Spray Gun. Even though you may be extremely careful with your washing tools, accidents happen. And your spray gun can come out of your workshop broken. And if not broken, with time your spray gun can wear out. In either case, Interstate Pneuamtics spray guns is what we recommend. You can use this replacement spray gun on pressure washers rated upto 4000 PSI. It comes with a Trigger Lock to prevent accidental spraying when not in use.