These push-to-connect fittings are manufactured in gray acetal, with food grade nitrile O-rings, from FDA compliant materials. They are made for use in a variety of water, coffee, beverage and other fluid applications. They are suitable for compressed air and inert gas applications, including CO2, pneumatic and vacuum applications and connect and disconnect without the use of special tools. They can be used with plastic tubing (polyethylene, nylon and polyurethane) and soft metal tubing (brass, copper, mild steel). An insert is recommended for soft or thin wall plastic tubing.