the retaining rings are not shown in this figure to allow a clearer description of other components of the base assembly 10 as noted above the shank 34 of the wear sleeve 30 is inserted into the bore 26 the bore 26 has a counter bore 70 in the rear face 54 of the holder portion 24 also shaped into the rear face 54 is a radial slot 72 an axial slot 40 is defined in the rear section of the shank 34 of the wear sleeve 30 the axial slot 40 corresponds to the radial slot 72 of the holder portion 24 a keyed ring 60 comprises a ring section 62 and key section 64 the keyed ring 60 is sized to slide axially over the shank 34 of the wear sleeve 30 and into the recess created by the shank 34 and the counter bore 70 as seen in fig2 the keyed portion 64 extends radially outward into the radial slot 72 of the holder portion 24 the keyed portion 64 also extends radially inward into the axial slot 40 of the shank 34 of the wear sleeve 30 this configuration interlocks the shank 34 with the holder portion 24 and prevents rotational movement of the wear sleeve 30 placing the keyed ring 60 at the rear face 54 of the holder portion 24 keeps it in a protected location away from the more severe abrasive effects at the front of the wear sleeve 30 and holder portion 24 in.