These push-to-connect fittings are manufactured in white polypropylene, with food grade EPDM O-rings, from FDA compliant materials. They are made for use in a variety of water, coffee, beverage and other fluid applications to connect and disconnect without the use of special tools.They can be used with plastic tubing (polyethylene, nylon, polyurethane) and soft metal tubing (brass, copper, mild steel). An insert is recommended for soft or thin wall plastic tubing. They are NOT suitable for compressed air applications (use our acetal fittings instead).