Wolf Tooth 42T GC Shimano Revolution Bikes March 6, 2014 Wolftooth Cassette Cogs The GC42 cassette cog is so big that when machining the first batch, the machinist thought he made a mistake! If being big is cool then the GC42 cassette cog is the coolest cog around. This cog is made with the precision and finish our customers have come to expect from WTC, and this enables quite possibly the best feeling shift in the cassette. This cassette sprocket is for use only with Shimano brand 10spd XT & XTR cassettes. It is NOT compatible with any other brand or model of cassette. The shift points are properly timed to the tooth locations on the 36t Shimano cogs for optimal shifting performance. Use of this cassette sprocket requires removal of the 17T cog & spacer from your cassette. A longer (25mm) “B-screw” is provided in the package. In most cases, this longer screw will need to be used with Shimano derailleurs to obtain the needed clearance. It is usually not needed with SRAM derailleurs. You may need a longer chain that what is presently on your bike. Make sure that when shifted to the 42T cog, there is still some amount of forward travel possible with the rear derailleur cage. This is especially important on bikes with rear suspension. We have tested with Shimano, KMC & SRAM chains – all function well. Compatible only with the following Shimano 10spd cassettes XT 11-36t (CS-M771) XTR 11-36t (M980) NOT compatible with SLX 11-36 cassettes because the 17t cog cannot be removed. For more information please contact your local dealer. Or us directly from our contact page.