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 chromoly axle and stainless cones; aggressive 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 Specifications: Position: Rear Brake Type: Rim Brake Axle Type: Bolt-On Hub Spacing: QR x 130mm (Bolt-On) Drive Type (Rear Hub): Single Speed Spoke Count: 32H Spoke Type: J-Bend Left Side Flange Diameter: 54mm Right Side Flange Diameter: 54mm Left Side Center to Flange: 33mm Right Side Center to Flange: 31.5mm Bearing Type: Sealed Cartridge Color: Black Weight: 158g