FYI, the new Sig Romeo 2 RD pistol sight *does fit* the MR920 and DR920 pistols. You will need to fit (sand down) one of the polymer recoil spacers to fit the gap behind the RDS which is approximately .075". I also have an Aimpoint ACRO P2 that has been direct milled to a Glock GEN 4 OEM slide. I like both of these sights, but I like the Romeo 2's window size more, it's seems a little more forgiving and faster to pick up the dot, *to me*.