Abstract: A fitting for connecting tubes which have circumferentially extending axially spaced ribs with recesses defined between the ribs comprises a socket member which advantageously has a cavity at one end of smaller diameter than a cavity at its opposite end which is adapted to receive the tube. The ledge is formed between the two cavities and a resilient member such as a sealing sleeve is disposed against the ledge at the inner end of the larger diameter cavity. The tube to be connected is positioned in the larger diameter cavity against the sealing sleeve such that its ribbed circumference underlies the slot in the larger diameter cavity which is closable by a locking fitting. The locking fitting includes an inner end which is adapted to be secured to the socket and which in one embodiment includes a bending strip which is affixed to the socket and supports the remaining portion of the locking lid at an acute angle with respect to the exterior surface of the socket.