Push-to-connect fittings offer secure connections and quick disconnection. Simply push tubing past the O-Ring to the internal tube stop-steel teeth on the collet grip tubing for leak-proof connections. To Disconnect, press collet against fitting body to disengage steel teeth-tubing slides right out. Fittings work with semi-rigid plastic (polypropylene, polyethylene, nylon) and soft metal (Brass, copper, mild steel) tubing. Adapters (sold separately) let you permanently modify basic fittings for customized installations. Polypropylene and EPDM materials meet NSF 51, and NSF 61 requirements for food-grade applications, and is compliant