I have used both Lancer and Thril magazines for my MPX K. I like the way the newer Thril mags look but I have some issues with them. One mag I had to return since it would prevent the bolt from going into battery. The other Thril mags did the same thing but stopped after they were left loaded for a few days. I never had any problems with the Lancer mags.Which MPX Mags Are More Reliable?Lancer (old)Thril (new)OtherWhich MPX Mags Do You Prefer?Lancer (original)Thril (new)Other