Surly Splined Cassette Cog

Yes, this cog is designed to fit standard Shimano-splined freehub bodies. It is a direct replacement for single-speed conversions on most mountain and road hubs using that standard.

The wider base is a deliberate design choice to distribute the load across more of the freehub's splines. This prevents the cog from 'digging' into softer aluminum freehub bodies, which is a common issue with thinner, standard cogs.

No, this cog is specifically machined for 3/32-inch chains. It will not be compatible with the narrower chains used on modern 11 or 12-speed drivetrains.

While the cog is optimized for single-speed use, it features 9-speed spacing. This allows you to stack multiple cogs if you are building a custom drivetrain, though you will need appropriate spacers to keep them aligned.

The 415 hardened steel is significantly more durable than aluminum and offers superior wear resistance compared to standard stamped steel cogs. It is built to handle the high torque loads typical of single-speed riding without wearing down prematurely.