Guaranteed to remain readable for years. Stainless Steel Core won't rust! Most people put the Pet's name and phone Number or two phone numbers. I suggest using your mobile number rather than a home phone number because most people don't sit at home waiting for the phone to ring with a lost pet & we tend to keep our mobile numbers forever now. We can put 4 lines on the back of the tag. Once you make your purchase, you will be contacted so we can get the info you want on the back of your Pet ID Tag.