Originally Posted by
Lman
Attachment points for fenders~racks....danxs
5mm x 0.8mm is the most common for those mounts. 6mm x 1mm is also possible. Others may be unthreaded to use a bolt that passes all the way through the fitting. Older USA-built bikes may have SAE spec fittings. And older British bikes may have Whitworth spec fittings.