I had the same problem with an aftermarket magazine I bought at a gun show for my p 35. I don't know the mfgr. The magazine catch inside the magazine well was too short to catch the magazine and the mag was looser than the original and would fall out. I just opened up the 'thickness' of the magazine with a screwdriver a little so it fit a little tighter and the magazine catch inside now catches the hole in the magazine. Works fine. Oh, and the follower is different from the original but it still works.