R stands for rally Asymmetric rims and same length spokes for nearly even left/right tension 30mm ID, 34mm OD double wall 6069 aluminum rim (40% stronger than 6061) Tubeless ready rims, tires mount easily without a compressor Wide bearing stance for reduced radial loading Hub end caps are easily replaced to fit virtually any axle standard 120point, 6x3-pawl system engages every 3 degrees International Standard 6bolt disc rotor mount Built with double butted spokes and alloy spoke nipples Choose SRAM XD or Shimano Micro Spline freehub