CAMPAGNOLO RD21 EKAR 1x13EKAR 13 speed derailleur is custom designed to work specifically in conjuction with the EKAR drivetrain One specific function allows it to be fine tuned for optimal performance Parallelogram 2D trajectory designed to work flawlessly with larger cog jumps and EKAR cassettes Redesigned mechanical clutch system works to absorb chain shock on any terrain Differentiated pulleys offer better control and retention of the chain