OC Tactical is now carrying magnets that are meant to help you organize your ammo cans. They are printed with various calibers or other related items like “Mags” or “Range Gear” so that you can identify what your ammo cans are holding at a glance. They are very inexpensive and not semi-permanent like a sticker. Everyone say it with me. “Why didn’t I think of that?”
Check out the Ammo Can Magnets from OC Tactical.