EXCELERANT HUB R-12 The Excelerant R-12 rear disc brake hub has not just 2, but 4 sealed bearings to bring that stable and smooth action we all need and love. This oversized 12mm bolt on axle hub was engineered with a multi-pawl unison engagement freehub and an oversized aluminum hub shell for superior durability and stiffness. New for this year are the 36 flanged hole option and the powder-coated white option. ................................................................................................................................................................................ Disc brake compatible 8/9-speed rear hub Body: forged and CNC machined 6061-T6 heat-treated alloy with standard disc brake mount Cassette: 7075-T6 heat-treated alloy, HG-type cassette body (12T) Axle: 12mm Size: 135mm / 32 or 36 holes Surface finish: sand-blasted anodized with CNC refinishing Bearings: 4 sealed bearing design Color: black and white Wheel building specs here