Standard capacity was 15rd, but somewhere along the way Mecgar figured out that they could easily get 17rds inside the mag body without spring bind if they designed things properly. So the 15rd mags are for NJ and those who like things 'stock', and the 17rd mags are for those of us who believe that a large grip frame should give as much capacity as can be made reliable.Is there any reason to go with a 15 rd mag rather than a 17 rounder? I'm guessing the 15 rd mags are for NJ residents... but maybe I'm missing something.
I use Ram-Line mags that hold 18 rounds. They have worked great. My only complaint is that the rounds rattle in them, but not in the factory mag.