In all due respect, I wouldn't even attempt to tattoo numbers & letters on an animal's ear using human tattoo equipment. For one thing, lot's of hair in way on animal's ear. Second thing, you are looking at minutes using human equipment. The special tattoo kits for animals are very inexpensive and once the animal is in a chute, headgate, or other restraint, the actual animal tattoo equipment probably takes less than 15 seconds to do...and, all the animal numbers & letters are pre-fixed so you'll always get a clear, legible impression. ;-)