hello. I'm tring to find a compatible sprocket for my chain. I need to know what these abbreviations mean here: http://www.ebay.com/sch/i.html?_odk...ket+40+3/4.TRS0&_nkw=sprocket+40+3/4&_sacat=0 For example, what does a 40B10H-3/4 mean? Or a 40BS13 3/4"? I think the 40 represents the chain # it supports, but I what numbers represent the size of the gear? Is it radius or diameter and what unit is it in? Thank you!