FEG brings up a point.
I've had good luck with Pro-Mags in full-size 75Bs, in my 85 Combat, in my Compacts, and in my 75B SA. I've also had good service from them in S&W 669s, in Berettas (92 Vertec), and in a Kel-Tec P-11, which accepted 15-round S&W Model 59 mags. Some of my friends have had good service from Pro-Mags in their SIGs.
Others, shooting other guns have had horrible experiences.
It really depends on the specific model of gun. Pro-Mag seems to know how to do it right for some guns, but not others. (Their mags for Lugers are horrid; Mec-Gars are the only ones I've found that work as they should in a Luger.)