A tube coupling comprising having a coupling body with an opened ended throughway to receive a tube. A collet is located in the open end of the through way having a ring and flexible arms extending generally axially of the ring into the throughway. The throughway has a tapered surface convergent towards the open end and the collet arms have heads at their distal ends for engaging the tapered surface and a tube extending through the collet into the throughway to be compressed against the tube by the tapered surface with outward movement of the collet with respect of the throughway to secure the tube in the throughway. A collet lock is formed on the collet, and the collet has a locked rotary position Either the body or the collet has a cam surface and the other has a cam follower.