Cassette Cogs

40T GC Cog for ShimanoThe GC line of cassette extender cogs allow you to modify your 10 speed cassette into a wide range cassette.  To achieve the optimal shifting, the GCs are optimized for Shimano or SRAM cassette. Compatibility:

Compatible with Shiman

42T GC Cog for ShimanoThe GC42 cassette cog is so big that when machining the first batch, the machinist thought he made a mistake!  The GC line of cassette extender cogs allow you to modify your 10 speed cassette into a wide range cassette.  To achieve t