A tube fitting of the push-pull type wherein the tube end is connected to the fitting by a simple inward insertion thereof, and withdrawal of the tube is effected by a simple withdrawal movement thereof upon manual rearrangement of the fitting components. The fitting includes a spring finger locking element adapted to engage the tube end when inserted and effectively prevent outward axial withdrawal movement of the tube end. A manipulating device is provided for selectively disengaging the spring finger from the tube end to permit axial withdrawal of the tube end when desired. The disengaging device is a one-piece element and is associated with suitable seals for providing an accurately preselected prestressing thereof against the tube end and body to provide an improved seal of the tube end to the body. The spring fingers are defined by an annular element. In one form, additional structure is provided for providing different spring constants relative to axial outward and inward movement of the spring fingers.