Completely unimportant and probably weird question, but what does PU stand for?I'm confused about what you mean. A tier between RU + NU wouldn't exactly work out, because the only place for Pokemon with low usage in RU to go is NU. PU is a tier that has been talked about being implemented, which is basically the NU of NU. But support hasn't been high enough to make it official. I think RU was created because of a) the large about of new mons, and b) popular support, two things that are currently lacked for PU, at least to my understanding.