MTM Hydro's Plated Steel Plugs offer a a fast and economical QC system for your high pressure joints. As a rule of thumb, MTM Hydro 1/4" fittings are normally found at the end of the pressure washing system on the spray wand or outlet of the spray gun. When purchasing Plugs and couplers the Male model has exposed threads while the Female version has threads on the interior of the fitting. See image for reference.