The Wolf Tooth Aluminum Single Speed Cogs will fit any Shimano-type freehub and feature extra tall teeth for reliable chain retention when using chain tensioners. Machined from 7075-T6 Aluminum billet for the best combination of light weight and high strength. They are reversible and feature a 4.5mm width at the base that won't dig into your freehub body. Wolf Tooth Aluminum Single Speed Cogs Features These will fit on any Shimano-type freehub spline (geared or single speed) Designed to work with any chain Tooth width optimized for 9-,10-, and 11-speed chains Wolf Tooth Aluminum Single Speed Cogs Specifications Weight:  22T - 23g20T - 20g, 19T - 18g, 18T - 16g, 17T - 15g, 16T - 11g Material: 7075-T6 aluminum Made in the USA