A tube coupling includes a body (1) to receive a tube (22). The body has lateral recesses (12) extending outwardly from an internal wall. An O-ring (3) is retained by the body distally of the recesses. A collet (5) includes a ring (6) and collet legs (7) to be received in the lateral recesses and having a tooth (8) facing the passageway. Proximal movement of the collet with respect to the body causes the fingers to deflect inwardly. A tube support (10) includes a ring (12) and has a key to align with the body. Castellations (13, 14) extend proximately from the tube support ring and are complementary to the collet legs to align the collet with respect to the body as the collet is inserted into the body.