I have a couple dozen cartos in circulation at any given time. I have abbreviated all of my flavors. I write on my black cartos with a silver sharpie, and I write on my silver cartos with a black sharpie. Then a tiny piece of scotch tape to cover it so it doesn't rub off. It hardly shows. I also put black sharpie dots near the end of my eGo batts right next to the eGo lettering to denote 1, 2, 3, etc...and a tiny piece of tape so I can keep them in an even rotation. It's not even noticeable.