This is a 1/4 inch male pipe thread X 3/8inch O.D. tube size push in quick connect elbow fitting. Commonly used as an outlet fitting on many makes of reverse osmosis systems. Connects the 1/4inch MPT thread on inline post filters and canister filter housings. Ultima Part number JG12. Includes locking clips to prevent accidental release of the connection. You can also replace the O-rings if a leak occurs.