Most of my magazines are USGI. I received 5 MagPuls from S&W as part of my purchase of a M&P 15. I compete in NRA high power matches & use USGI 20 round mags in my match gun. I bought them used at least 10 years ago and must have put over 2000 rounds through each, on average. They still function 100%. The MagPuls are still on the shelf. I'll use them when the others wear out.