Long lasting 7075 alloy single speed cog fits Shimano™ cassette body. An offset thickness increase from the teeth to the spline keeps the cog from damaging alloy cassette bodies and provides the option to run the cog in either direction for improved chainline. Uses Sram PC-1 single speed chain. Available in 17, 18, 19, 20, 21 or 22 tooth. Selection may be limited.