5-arm, 110 mm bolt circle, Aluminum 7075 T6, black SB-packed, suitable for Stronglight, Shimano, SRAM Road cranksets The Revolutionary Chainrings from O.Symetric Non-circular shape for a 10% performance increase, better acceleration. 10% reduction in muscle lactic acid production, no other chain length necessary. Successes with O.Symetric Chainrings: Tour de France 2017 - Winner Christopher Froome Tour de France 2016 - Winner Christopher Froome Tour de France 2015 - Winner Christopher Froome Tour de France 2013 - Winner Christopher Froome Tour de France 2012 - Winner Bradley Wiggins Tour de France 2012 - 2nd Place Christopher Froome Vuelta 2017 - Winner Christopher Froome Olympic Games 2012 - Winner Individual Time Trial Bradley Wiggins Gold Medal Olympic Games 2012 - 3rd Place Individual Time Trial Christopher Froome Bronze Medal Ironman Abu Dhabi 2014 - Winner Tyler Butterfield Ironman Hawaii 2013 - Winner Frederik Van Lierde Roc d'Azur 2013 - Cross Country Winner Miguel Martinez Number of teeth 38 Type Article Attachment 5-hole Main color black Bolt circle 110 mm Rear gear stages 10-speed, 11-speed