Surly Ultra New Rear Hubs, Non-Disc. Features: Axle is quick release and bolt-on compatible Stainless 6mm bolts are included; quick release skewer is NOT included 6061-T6 forged hub shell (same as the Surly New); 6901 bearings 4130 CroMoly axle and stainless cones; agressive knurling on cones and bolt caps for reduced slippage New axle/cone system uses uses a specific shouldered axle that allows the hubs to be completely adjustment free and simple to service Specs: Center to Flange, Left37.5 Hub Drilling32 Flange Diameter, Left54 Cassette Body TypeThreaded Standard 1.37" x 24tpi Center to Flange, Right38.5 Weight337g ColorBlack Defined ColorBlack Spoke InterfaceJ-Bend Flange Diameter, Right54 Hub/Brake CompatibilityRim Brake Skewer IncludedNo Rear Axle10x1 Threaded x 135mm