Whether we are converting or just upgrading, the Wolf Tooth Alloy Single Speed Cog is a great addition to any single-speed bike. The Wolf Tooth Alloy Single Speed Cog is available in various colors and tooth counts to fit our needs and is optimized to work with 9-12-speed chains with Shimano HyperGlide-style freehubs. The cog is made of high-quality 7075-T6 aluminum alloy for durability and a lightweight design, with the 18-tooth cog coming in at only 19 grams.