When supplied with a finished bore a set screw is located over the keyway and through the base of the groove marked with a single asterisk* 

All but the smallest grooves are machined with profiles to accept both standard V-Belts and where the diameters allow Wedge Belts. Small diameters have a  truncated groove profile and can only be used with classical V-Belts. Diameters marked with a double asterisk** have truncated grooves.