Rain Bird 1800CAPS Spray Head Cap for 1800 Series Sprinklers. Use this threaded cap to quickly and easily cap off pop-up spray heads when converting to Drip irrigation. No digging required to cap a Rain Bird 1800 series sprinkler; simply twist off existing cap, remove the internal mechanism and screw on the new cap. Gasketed cap provides a leak-tight seal of any unused heads on the zone.