The first generation of black plastic follower magazines were less expensive, thinner and cheaper but did actually work. The second generation had red plastic followers and were even cheaper but I will say most of them work too. After that, fast forward to the current crop of cheap crummy magazine's that 9 out of 10 times will not work in older guns and many will not even fully seat in older model 41's.According to Standard Catalogue of S&W 5th edition (which I highly recommend), 1985.