The John Guest 3/8 in. x 3/8 in. Push-to-Connect Male Fixed Elbow, Black (10-Pack) fittings are manufactured from U.V. stabilized black polypropylene and equipped with EPDM O-rings utilizing John Guest's push-fit technology to make easy, reliable, leak-free connections. They have been developed to satisfy the compatibility needs for a wide range of applications and can be used on plastic or soft copper tubing. To make a connection, the tube is simply pushed in by hand; the unique John Guest collet locking system holds the tubing firmly in place. Disconnection is just as easy and requires no special tools.