Wolf Tooth 16T Cog for use with Shimano or SRAM GC Cogs

Here are the transitions WITHOUT the 16t cog (4 tooth max jump):

Remove the 15t -> 11-13-17-19....

Here are the transitions WITH the 16t cog (3 tooth max jump):

Compatibility - any cassette that is compatible with the GC40 or GC42

Note: the GC 42 is not compatible with 2011 or older SRAM rear derailleurs due to the location of the upper jockey wheel. The best ways to tell the vintages of your rear derailleur is 1) If you have a type 2 (clutch type) rear derailleur it is 2012 or newer and 2) the upper jockey wheel on 2012 and newer rear derailleurs are offset from the derailleur cage's axis of rotation. It is difficult and sometimes impossible to get satisfactory shifting with the 2011 or older SRAM rear derailleurs so we do not recommend using the GC 42 if you have one of these. The GC 42 works great with the newer SRAM rear derailleurs however.