Two sides to this story. Used to be a ball with say greater than a 5" pin (now called a pro pin) or a ball where the cg was significantly out of line relative to the mass bias and the pin (now called pro cg) were called "blems" or "x-outs" or "seconds" etc. I think Storm was first with the "Pro pin, Pro Cg" terms. The claim is PBA players can drill these balls for reactions that you can't get with, let's say, non pro pin or pro cg balls. Is this really true?? I can't answer that. Perhaps if you ask in the Storm forum Jeff Carter can answer or try BrunsNick in the Brunswick forum.