People hate on ProMag, but I've had 3 of em - 1x Rollermag for an AR-15, 1x 5 rnd steel flush fit AR, 1x 10 rnd 1911 mag - all have worked fine in my ARs, 1911, & both Hi-Points.
They must be doing something right, they've been in business for a long time & keep expanding their line. CMMG uses them as OEM for one of their 5.7x28mm guns.