These nozzles help to accommodate a machine requiring a larger or smaller orifice which is estimated in the ranges of flow exceeding 4 gallons per minute or below 2 gallons per minute. The purpose of these various orifices is not to increase or decrease pressure but to match as closely as possible, to the recommended orifice size for your machine. When attempting to determine the correct orifice size use a nozzle selection chart with your machine specification of GPM and PSI. Specifications: