Abstract: An improved plastic push in tube fitting includes a plastic body, an elastomer o-ring for sealing, and a plastic collet. The collet and o-ring are disposed in the body such that a tube can be pushed into the body through the collet and o-ring and held against withdrawal from the body by the collet. The collet is formed entirely of plastic and has a plurality of circumferential sections for encircling a tube pushed into the body. Each of the circumferential sections has a radially inwardly facing circumferential tube gripper. The tube gripper is formed by a ramp which faces a tube being pushed into the body so that the collet will encounter the ramp and move the circumferential sections radially apart. The gripper also includes a circumferential surface which faces away from a tube being pushed into the body. The circumferential ramp and the circumferential surface form a gripper edge at their junction and this edge engages and holds a tube pushed into the body through the collet.