The message .com
from "TC" contains these words:

I have snapped a bolt (from a seat post on my bike) so need a
replacement but don't know what to get. Presumably the bolt length and
shaft width and also information about the thread - how do I do find
that out?

It's almost bound to be metric if it's a recentish bike. Probably 8mm.

--
Skipweasel
Pay no attention to that man behind the curtain.