Ordered one of these on a friend's recommendation. Your personal details are fully customisable and etched on to a small metal tag. This sits within a velco strap which simply wraps around one of the straps on your helmet.
It's a great little product - you don't notice the tag when worn - and a nice safety feature, as it means I don't need to take ID with me along for my rides. Look out for discount codes on the website as they do pop up from time to time.