Wheels Mfg. SOLO-XD and SOLO-SPLINE Single Speed cogs are constructed with high-end 7075 aluminum and designed with narrow to wide alternating tooth pattern allowing for superior chain retention. Cogs are optimized for use with Wheels Mfg. SOLO-XD XD/XDR and SOLO-SPLINE Single Speed Conversion kit carrier systems only.Crafted with high-end 7075 aluminum for light weight and extreme durabilityCogs are optimized for use with Wheels Mfg. SOLO-XD XD/XDR and SOLO-SPLINE Single Speed Conversion kit carrier system onlyDesigned with narrow wide alternating tooth pattern allowing for superior chain retentionFits 9, 10 and 11-speed chainsCompatible with 12-speed SRAM Eagle, KMC, SRAM Road and SRAM T-Type Transmission flattop chainsWill not work with 13-speed Campagnolo or 12-speed Shimano HG+ chainsItem SpecificationsDefined ColorBlackMaterialAluminumTooth Count21 Wheels Manufacturing Solo-XD and Solo-Spline Cog Driver and Single Cog UPC: 810124712891