Surly Track Cog Lockring. Precision CNC machined Stainless Steel English type L/H threads &40;1.29&34;x 24t&41; Fits most Track hubs except Campag &40;1.32x 24T LH&41; or French &40;33x 1mm LH&41; Silver. Note: General Fixed cog check:for correct fixed use the fixed cog should NEVER move on the hub when pedal force is applied in both directions.i.e. if the cog moves then something is wrong. Continued use with a fixed cog that moves will result in damage to the hub.