This question is probably for guys like me, whose screen name isn't so obvious.
So, as a former Honda parts guy, it was clear to me what to use. All Honda parts have 3 sections. The first is 5 digits, telling what type of part(air filter, gas tank...). The second part is a 3 digit number or letters denoting what bike the part was originally designed for. The center code "333" is for my bike, a CB350F. And to finish the description of the part number, the third part is for many things like color of painted pieces, supercede's, manufacturer changes, and jet sizes. Standard screws, bolts, and nuts have a totally different numbering system.
The avatar? That's a story for another night, kids.