The Radius Spindle Spacer 3/4″ ID x .970″ OD x 1/4″ thick Aluminum Radius spacer commonly the first spacer on the spindle axle shaft closest to the spindle. 

High-quality spindles like the EC spindles have a generous radius riser to reduce stress under load. Lower quality spindles usually have premature spindle breakage due to the lack of this riser radius.