Wolf Tooth RoadLink: For Shimano Wide Range Road Configuration. Roadlink Rear Derailleur Part

The RoadLink is optimized for use with ten or eleven-speed 11-36t and 11-40t cassettes

11-42 or 10-42 setups are not supported

Works with all 10-11 speed Shimano and SRAM Road Derailleurs

Best used with Single or Double Setups - see manufacturers site for more details