Honeywell S06K-1/4NPT BlankingPlugW/Oring NK300S

The NK300S is a (re)filling combination valve that contains an integrated pressure reducing valve, strainer, double check backflow preventer with air vent (to protect potable water supply against back flow of heating water into supply pipe), two shut-off ball valves, pressure gauge, and conveniently located test ports for easy inspections and check out. All the needed devices for refilling a heating system are contained.