I havent put more than 2 tags on the rubit. Its a normal ring, so you can fit several with no problem. The pictures that Amy posted with her dogs wearing them is size medium. Not a huge difference in the Rubit size and they dont weigh hardly anything. I have my 3.5lb boy in the small and the others wear the medium. They are both small clips.
I will take some more pics and post later. Thanks everyone!