groove 38 of the drive sleeve 30 in one preferred arrangement the outer surface of the part nut 40 and an internal surface of the main housing 4 are keyed together by way of splines 6 to prevent relative rotation between the part nut 40 and the main housing 4 while allowing relative longitudinal in movement between these two components a dose dial sleeve 70 is provided outside of drive member 30 and clutch 60 and radially inward of the main housing 4 the dose dial sleeve 70 comprises a distal end and a proximal end a helical groove 74 is provided about an outer surface 72 of the dose dial sleeve 70 the main housing 4 is provided with a window 44 through which a part of an outer surface 72 of the dose dial sleeve 70 may be viewed the main housing 4 is further provided with a helical rib 46 adapted to be seated in the helical groove 74 on the outer surface of the dose dial sleeve 70 in one preferred arrangement the helical rib 46 extends for a single sweep of the inner surface of the main housing 4 returning to fig1 2 a dose dial grip 76 is disposed about an outer surface.