number(s) for Ball mason jars, not the bottom mold No.s

[Danny Edwards]

I'm seeing posts and auctions saying "Ball Perfect" #4, or #14 and so forth. My searches for the meaning of these have not been fruitful. i assume it is the type of jar specifically, and was hoping someone could point me in the right direction. I have a decent amount of old jars, all types, and am looking to sell them for my friend. Thanks, love this site!!!