I notice when many writers in the forum are describing a bicycle part, they use a name and a number. For example, Ultegra FD 6400, or Ultegra FD 6406 (just made those numbers up, I think you know what I mean) It seems that the part number is important for parts compatibility.
I know the name but not the number for the parts on my bike. Where can I find out the parts number? It is not included in the "Specs" description on the bike maker's web page. I don't know where else to look.
Also, how do I find out which part number is best? For example , Which is better, a Mavic wheel rim A719 or a Mavic Ex 719? What about a Mavic 721? How or where would I find that out?