The Kleinn FIT89 complete fittings kit bundles the 1/4" NPT fittings used in HK8 or HK9 Problaster Horn Kits, including the specified pressure switch, safety valve, drain cock, compression fitting, hex plug, plus a momentary push button and thread sealant. It’s intended as a single-source set to assemble or service those Problaster horn configurations.
Kleinn HK8 Complete Set of Fittings