is shaped positioned and arranged to allow it to slide through housing member 102 which in one example has a smaller inside diameter than the outside diameter of collet 202 in one example this is accomplished by machining individual collet fingers 501 which can be viewed as individual cantilevered beams that will deflect under load this deflection allows collet finger 501 to deflect inward and pass through a smaller diameter restriction of housing 102 and spring back to the original outside diameter past the restriction in one example an additional feature of collet 202 is that is can support longitudinal loads once engaged in a suitable retaining groove in one example the length width and thickness of collet fingers 501 are selected to match its operational requirements as these parameters determine the stress induced in individual collet fingers 501 when deflected inward while shifting the treatment valve 100 the combination of those characteristics and the yield strength of the material used to construct collet 202 are selected to ensure that collet finger 501 is flexible enough to spring back after being compressed which is to say that the stress due to the applied inward deflection does not exceed the yield strength of the material used to construct collet 202 in one example collet finger 501 is of substantial enough strength to withstand the longitudinal loads applied during operation fig5 b shows a cross sectional view of one example of the collet fig5 b shows the collet thread 502 used to fix collet 202 to inner sleeve 201 at inner sleeve thread.