We're getting a working cocker spaniel soon and I'm looking at ID tags. Our puppy's parents are both quite small, so I don't want to buy a tag that's going to be too big/heavy and get in the way or annoy him. How much does size matter? I'm thinking of getting a 33mm one or a 39mm one. How much difference will it make to our pup? I really want to be able to fit all the crucial information on there and for it to be easy to read, and I want the tag to be durable. These are the tags I'm currently looking at, but I'd appreciate any recommendations anyone might have for good tags! Also, how many tags should I buy? Is it enough to have one for the collar and one for the harness? Or is it wise to get spares?