154 the clicker 50 u2032 is located adjacent the second flange 34 u2032 of the drive sleeve 30 u2032 the clicker 50 u2032 includes at least one spring member not shown the clicker 50 u2032 also includes a set of teeth not shown having a triangular profile disposed towards the second end of the drive mechanism when compressed the at least one spring member of the clicker 50 u2032 applies an axial force between the flange 34 u2032 of the drive sleeve 30 u2032 and the clutch 60 u2032 the outer surface of the clicker 50 u2032 and an internal surface of the internal housing 154 are keyed together by means of longitudinally directed splines to prevent relative rotation between the clicker 50 u2032 and the internal housing 154 while allowing relative longitudinal movement there between the clutch 60 u2032 is located adjacent the second end of the drive sleeve 30 u2032 the clutch 60 u2032 is generally cylindrical and is provided at its 39 first end with a plurality of teeth of triangular profile disposed about the circumference not shown that act upon the teeth of the clicker 50 u2032 towards the second end of the clutch 60 u2032 there is located a shoulder 158 the shoulder 158 of the clutch 60 u2032 is disposed between the internal housing 154 and a radially inwardly directed flange of the dose dial grip 76 u2032 described below the shoulder 158 of the clutch 60 u2032 is provided with a plurality of dog teeth not shown extending in the direction of the second end of the drive mechanism the clutch 60 u2032 is keyed to the.