I have a flash drive based one so that in an emergency they pop it into a computer and everything comes up. I wear it because I'm on an MAOI which interacts with a lot of drugs and I have a lot of drug allergies. It's really convenient; I used it once when I went into the ER with a serious stomach bug and a head to toe rash and since they immediately started IV benadryl I was confused and couldn't remember my meds so it was nice they could pop it in and get it off that. I need to update it in fact; I'm glad you reminded me. I also have a plastic tag on my keychain that says to see my necklace in case someone wouldn't identify it as a medic alert (it has a symbol on it but just in case).