An annular having a central bore includes a conical surface concentric with the bore such that the conical surface has a peak, an inner trough and an outer lip and the inner trough is adjacent to the central bore. A retention groove located under the outer lip has an outside diameter that is less than the lip outside diameter. A tapered reflective face extends outward from the retention groove. When a code wheel disc having an inside diameter that is smaller than said lip outside diameter is pressed onto the conical surface, the difference in size of the lip outside diameter and the disc inside diameter promotes a deflection of the disc which forces it to conform to the tapered reflective surface.