D. THE FITTINGS ARE MANUFACTURED IN WHITE POLYPROPYLENE WITH FOOD GRADE EPDM O-RINGS..John Guest Polypropylene Faucet Connector 3/8'' x 7/16''-24 UNS - Pack of 10 THEY HAVE BEEN DEVELOPED TO SATISFY THE FILTERED PURE WATER MARKET AND WIDE RANGE OF APPLICATIONS TO 1/2" O.