This is the Brake arm nut that is used to set adjustment on brake shoes
It is often lost or misplaced and can become siezed making brake adjustment difficult if not impossible.
If you don't need one straight away, we suggest you grab one anyway and throw it in your toolbox for later use.
Note: suits most model ATCs with drum brakes.
Direct replacement for ATC200S/M 84-86, ATC250ES 85-87.