Promag = GARBAGE. Don't waste your money. Out of all of the models of firearms for which they make magazines, I have yet to hear of ANYONE reporting absolute success with them. They have been consistently making junk products for ages. About the only things I've seen that they make that are NOT total crap are maybe their now Rollermags for AR rifles/pistols, but even those are suspect because the springs (as most of their mags tend to be) are kinda wimpy. Well, that and maybe their magazine spacer adapters, and it's kinda hard to screw up a solid piece of plastic with no moving parts...
Stick with the factory Kel-Tec (Mec-Gar manufactured) magazines and you will have ZERO magazine-related problems.