Precision CNC machined Sprockets from heat treated Cr-Mo steel.1/8" "classic" Fixed size in Satin chrome or ED Black17T and larger are slotted to save weight1.37"x 24T Standard R/H threaded.Note: General Fixed sprocket 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 sprocket moves, then something is wrong.Continued use with a fixed sprocket that moves will result in damage to the hub.