Shimano Dura Ace FC-R9100 11 Speed Outer Chainring 54T-MX For 54-42TShimano Dura Ace FC R9100 11 Speed Outer Chainring This outer chainring can only be used with Shimano Dura Ace FC R9100 11 speed double chainsets with a 54 42T set up. The Shimano FC 9100 Chainring 54T MX for 54 42T is a tooth replacement or upgrade chainring that is compatible with the 11 speed Dura Ace 9100 series double chainset. Machined from aluminium and carbon, giving both greater rigidity and lighter weight than its predecessors, and with that