High-grade 420 stainless steel replaceable outer bands and billet aluminum CNC machined inner carriers. Cross drilled bands for increased ventilation Blanchard ground bands insure precise and even tolerance . Front rotors are drilled for standard H-D Bolt pattern 3-1/4" X 5" X 5/16". All center carrier are counter bored with 2.22 in. I.D. A reducer spacer is sold separately for 1.985 in. I.D