15 and engages the cover 15 such that the sleeve 175 is rotatable with respect to the bottom cover 15 but is not movable along the longitudinal axis 60 with respect to the bottom cover 15 in another construction the bottom cover 15 and the sleeve 175 are fixedly attached to one another such that both components rotate in unison about the longitudinal axis 60 as illustrated in fig1 the collar 170 includes a cylindrical outer wall 190 sized to fit within the first cylindrical wall 180 of the sleeve 175 to couple the sleeve 175 and the collar 170 for rotation the collar 170 also includes an interior surface 195 that is sized and shaped to inhibit radial movement of the split ring 165 and to hold the split ring 165 in its operating position in some constructions the collar 170 includes two or more key members not shown that extend along an axis that is parallel to the longitudinal axis 60 turning to fig1 the split ring 165 is illustrated as a single unitary component however the split ring 165 is preferably formed from two identical or similar half rings that when put together define the complete split ring 165 the split ring 165 includes two cylindrical wall portions 200 that are separated by gaps 205 and that extend from a second cylindrical portion 210 in some constructions two or more key slots 215 are formed in the cylindrical wall portions 200 a tapered bore defines the.