each collet 46 becomes aligned with the engagement profile 38 of the setting sleeve 34 each collet 46 will snap radially outwardly so that the radially enlarged portion 48 becomes disposed within the engagement profile 38 as shown in fig2 once the setting tool 42 is attached to the setting sleeve 34 in this manner the tubing string 40 is then pulled upwardly to cause the setting sleeve 34 to be moved axially upwardly within the enlarged diameter portion 28 of the bore 26 the collets 46 are not disengaged from the engagement profile 38 due to abutting contact between the stop shoulder 50 and the upper end 54 of the profile 38 the 38 the sealing element 32 is thereby axially compressed by the setting sleeve 34 and when axially compressed will be extruded radially inwardly against the tool body 44 of the production tubing string 40 the body lock ring assembly 37 will prevent the setting sleeve 34 from moving back downwardly with respect to the surrounding casing coupler 18 thereby preventing the packer device 30 from becoming unset because the components of the packer device 30 are retained within an enlarged diameter portion 28 of the casing coupler 18 the gap between the exterior of the tubing string 40 and the interior of the casing string 17 can be quite small for example in a casing string made up of 35 3 lb casing sections with an external diameter of 5 inches an interior diameter of 4 126 inches would.