I was introduced to the Rubit by Modern Dog magazine a few weeks before Christmas and low-and-behold it ended up in my stocking come Christmas Day! Cassie has several harnesses and collars that I switch out depending on the day's activity. It was a real pain having to switch out her dog tags each time or simply make her wear multiple collars because I was too lazy to do so. Now, I just put all of the tags on this carabiner style clip and pop it onto whichever collar or harness she has on. The only draw back I've found is that they do jingle-jangle a bit more than normal, but this hardly outweighs the convenience and safety.
I can put her id, rabies, dog tax and her microchip tags on any collar in a second, which makes me feel safer taking her out. I have the large round Rubit, which cost only $8 and was worth every penny. They can be purchased directly from the Rubit source site or on Amazon. The Rubit site has a bigger selection than Amazon. It's a must for any busy pet owner.