Keeping uphill gearing on your mountain bike without having to plunk down for a 50+ cog and fancy colors to upgrade your workhorse 10-speed drivetrain is now easier with the Shimano CS-M4100 Cassette. With terrain specific options, the 42-tooth or 46-tooth, you can ride long tempo climbs or have an aggressive hill crusher. And the 10-speed design still allows a fast downhill 11-tooth cog to motor back to the trailhead.