... for the G1/4 the tooth type structures, unions, more convenient, can match fast by type nut and pipe plug 3, ... connectionRed: the positive, black: negative, yellow: pulse signal Water flow sensor (water flow sensor) and flow switch (flow switch) outlet terminals ... piece two kind of material, mainly for the water heater, wall-hang boiler, water machine. NOTE: OKD-HZ41FB water immersion sensor ROHS POM