Wolf Tooth Single Speed Aluminum Cog These Wolf Tooth aluminum single speed cogs feature extra tall teeth for reliable chain retention when using chain tensioners. Features Crafted with strong and lightweight premium 7075-T6 aluminum Optimized for use with 91011 speed chains but suitable for use with some 12-speed chains Reversible and 4. 5mm wide at the base to help prevent cog from damaging your freehub body Fits Shimano Hyperglide style freehub splines Not compatible with Shimano Microspline or SRAM XD freehubs Not compatible with Campagnolo 13-speed chains | Wolf Tooth Components | Silver Cog Silver 19T