@jys1011:
Andrea-do you mean that you keep these on all day & it doesn't cause their fur to rub off??
yep, they wear them all day, and night. What I have found with the Nick collars is that they are loose enough they don't wear the hair much. I went back and forth for years ( you will notice on the website there are lots of pics of them without collars) about whether or not they should be nakie. Their neck hair *does look better when they haven't been wearing collars, but IMO the likelihood of them getting loose, and being unidentified was far greater, and scarier to me than having some worn hair. That being said, if we are coming up to a big show, I may take the dogs collar off for a few weeks before the show, so the hair can grow in.
Also, I found when we started having some fights amongst our girls a few years ago, a collar was a necessity for separating them without getting bitten
We use brass ID tags that bolt right to the collar, rather than hang, because I *don't like the idea of them getting the tags caught in teeth and mouths while playing.