The Milton Industries MIL-1109 Milton -5 1/4" NPT Polycarbonate Piggyback Filter Regulator is a replacement filter regulator for Milton Industries' MIL-1109 Milton water filter. The Milton Industries MIL-1109 Milton -5 1/4" NPT Polycarbonate Piggyback Filter Regulator is made from polycarbonate and is designed to fit onto the Milton Industries MIL-1109 Milton water filter. The Milton Industries MIL-1109 Milton -5 1/4" NPT Polycarbonate Piggyback Filter Regulator helps to regulate the flow of water through the Milton Industries MIL-1109 Milton water filter and helps to ensure that the water is clean and safe to drink.