completely around the circumference of the adaptor it is understood that it could be separated into two or more segments that are spaced apart around the inner wall the inner wall 60 and the outer wall 70 are spaced apart to transfer the stress and or strain away from the magnetic ring as shown more clearly in fig2 b which depicts a cross section a a of fig2 a the groove 50 is almost u shaped or u201c cup u201d shaped the groove 50 can be formed using various methods such as machining casting extruding and stamping with the stamping process being preferred fig2 c which depicts section b of fig2 b in more detail reveals that the inner wall 60 also includes an undercut 90 to greatly reduce the stress and or strain applied to the magnetic ring fig3 a depicts yet another embodiment of the adaptor which is sized to fit against an inside wall of the magnetic ring again the adaptor includes an outer wall 100 spaced from an inner wall 110 in this embodiment the inner wall 110 includes six slots 120 it is understood that the number of slots could vary depending on among other things the size of the adaptor the slots 120 are u shaped or rectangular shaped as shown or may be presented in other similar shapes the slots 120 serve as alignment features when assembling the adaptor on the shaft for example the slots can be aligned to an assembly tool used to assemble the different components which is in turn aligned to another component on the shaft the inner wall 110 also includes a plurality of grooves 130 or splines like those described previously which provide an interference fit to a shaft the grooves 130 serve.