This chemical injector allows you to apply soaps or strong cleaning chemicals, at low pressure through your pressure washer. These downstream injectors are designed to apply chemical only when running under low pressure (250 PSI or less). Use a large orifice nozzle to get the soap injector to work. 3/8" inlet and outlet. Applies soap at 50% or 5 to 1 ratio. 2.3 size is for use on pressure washer with 5 to 8 GPM.