I had one with a serrated metal ring on it. It would rip up most others. But there was this smooth black defense one I remember was really annoying to fight against. If you put razor blades in them they could fling each other.
It was another phenomena back then, right along with Pokemon and Yugioh. The original was cool, but the Metal Fusion series >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
omg i used to have so many growing up , i liked the cheap asian ones that had magnesium on the rings so when the beyblade touched something it wold spark and look pretty - so gay i was