The Pro 4 Rear hubs use a new 44 tooth ratchet mechanism. The flange diameter is increased, adding important stiffness to wheel builds. The machined hub shells are. Available with regular or Boost (148mm) widths. The 17mm axle runs on five cartridge bearings. Pro 4 hubs are 6 bolt disc compatible and available with 28,32 or 36 holes. Choose from six anodized colours. Rear hubs with Shimano compatible freehubs features a larger bearing, will be supplied ready to take 11sp cassettes. Pro 4 Rear hubs are available with the following axle conversions – QR, 10mm, 12mm and 142mm and with following freehubs –Shimano 8, 9, 10 and 11 speed, Campagnolo, Sram XD, Steel, and Hope versions. All these conversions and freehubs can be swapped without the need for complicated tools.