The smaller bearing on the  BEADING BITS makes a delicate inset at the base of the cut, giving you the advantage of an extra decorative option.BE SURE to keep the black bearing washer right side up to correspond with the bearing rotation when reassembling the bearing. Improper reassembly can cause the bit to unscrew.All CMT roundover bits have a 12,7mm (1/2") bearing diameter with the exception of the radius 28,6mm (1-1/8") and 31,7mm (1/4") bits which have a 19mm (3/4") bearing diameter. You have 13 different radii to choose from, the majority having 5 shank diameter options.All  are made of FATIGUE-PROOF® steel and have carbide-tipped cutting edges.