Hey Ray. I'm new to this forum, and so I hope-hope-hope you are still around to answer some procedural questions. I just now noticed that this thread is over two years old, so please be available. According to your stated specs. on the Glock replacement sight it was .018" wider than the slot on the Sigma slide. I'd like to know please, what was the geometric shape of the replacement sight's mounting post? Was it square, or rectangular, or some kind of polygon? And how Exactly did you file it to fit? Did you carefully take metal off both sides equally? The .018" greater thickness would equate to .009" per side. How did you accomplish taking the same amount of metal off each side, if that's what you did? Did you use a very fine file and a micrometer, or did you file it down by trial-and-error until it fit? Did you take metal off just one side or both? I need these details so I can make it work for me too just as it worked for you. Obviously the slot in the Sigma slide is that of a two dimensional cross sectional view of a cylinder. The post of the Glock aftermarket sight looked like a polygon, specifically hexagonal. Please, exactly how did you make it work? Thank you.