Orbit Underground Sprinkler System Winterization Kit, Brass Fittings, designed to fit on either a 1/2(in) riser or on a standard 3/4(in) outdoor hose faucet. It is used for blowing out an irrigation system. Simply remove a sprinkler head from the line and attach an air compressor via the adapter fitting. It fits most brands of air compressors and is for outdoor irrigation systems only.