What do you guys know about NPR?

Alright, I could definatly use some help here. I just Boughts a set of NPR Pistons and I'm a bit woried about the quality of them. It may just be me and my lack of knowledge though. For one thing, it dosnt seem as though the top part of the pistons are as wide as the bottom, but this seems to be the case on the OEM ones as well. For example, if I put the new piston into the cylnder upside down, it fits untill after the oil ring, and then stops. I'm getting the cylingers bored BTW. While the bottom is definatly a little bigger, it seems as though the top is not bigger at all. Wouldnt this cause problems with piston to wall clearance? Sorry if this dosnt make all that much sence, I just dont want to put inferior pistons in my engine and have it destroy itself. I'd get a picture, but I cant find my camara, i'll try to find it tomorrow.