Sights are not "drop-in" parts, especially for 1911 pistols. There are so many companies, large and small, manufacturing 1911 pistols today and they all have different ideas about dimensional consistency in the sight cut. The only way after-market sight manufacturers can provide you with sights is to manufacture their sights and hold their dimensions on the high side of the range commonly encountered. This means that to install sights on 1911s, you often have to "fit" the sight to the sight cut by finding the surface on the sight that is too big and filing it down until the sight can be installed and still fit tightly. Sometimes it's more than a single surface that Mfg: Harrison Design & Consulting