When ordering guides for rodbuilding projects, how do you know what size to order?

Example, I'm getting ready to order some snake guides for a bamboo refinishing project. The spacing chart for this rod suggests guide sizes ranging from 2/0 thru 2. OK, I can order them but what if I didn't have a spacing chart? I'm curious as to what size these snake guides are? Also I've seen stripping guides sized #8, #10 or #12 but again, I don't have an idea what they actually size to.

Is there any online chart available that shows what size these guides are in the different size ranges? Or, a chart that lists guide height or length or something like that?

I'm probably not asking this very clearly.