Sram force 1 rear derailleurthe sram force 1 rear derailleur implements all of the shifting accuracy and durability from the sram mountain bike derailleur design to provide exceptional off road performance for cyclocross use quiet and smooth shifting performancethe internal clutch design eliminates chain slack making it almost impossible for the chain to fall of the chainring whilst cycling a real benefit when riding on rough terrain it also creates a noticeably smoother quieter and higher