I'm using a Blackhawk Serpa CQC 1911 holster with my TM Hi Capa 5.1 and it's a very snug fit. That shouldn't be surprising though the holster was designed for a 1911 and the Hi Capa 5.1 is slightly thicker so the slides of the holster rubs against the slide/frame. What I like about this holster is I can run around all day and not have to worry about losing a mag.