Derailleur hanger extenders attach to the end of a rear derailleur hanger to allow use of large cogs on the rear cassette. Large rear cogs make it easier to ride up steep hills.
Extender 3001: Extender 3001 works with any 10- or 11-cassette rear drivetrain, and…
42-tooth maximum rear cassette (single chain ring)
40-tooth maximum rear cassette (Shimano and SRAM double chain ring)
36-tooth maximum rear cassette (Campagnolo double chain ring)
Extender 3002: Extender 3002 is designed to work with Shimano Shadow rear derailleurs (2013 and later). It will accommodate 10-speed rear cassettes 40-tooth or larger (eg, 11-40t or 11-42t). Extender 3002 can be used to replace the direct mount link on 2013 or later Shimano Shadow+ 10-speed rear derailleurs, and will reduce premature degradation of shifting.