Those are AWESOME! I'm getting two for my boys, I think. I just have to decide which would look best on Fozzie... Dublin, Galway, or Cork?!
I actually love collars made of that material. They sold a bunch at the feed store I used to work at, (I completely forget the brand) and those were actually a lot stronger than they look. As far as working for giant breeds or very strong breeds, I would probably be cautious. The sizes only go up to 21", so I don't think they're intended for giant breeds.