Most target-sighted 1911 pistols have a "BoMar" rear sight cut in the slide. Most combat-sighted 1911 pistols have a "Novak" rear sight cut. While you can get target-sight blades with tritium inserts OR you can get combat sights that adjust, you still can't make a Novak sight fit a BoMar cut or vice-versa (without welding & re-cutting). I've often wondered why no one (to my knowledge) makes a tough, fixed night-sight made to fit in a BoMar cut. It combat situations, clearing a jam with a fast, overhand rack of the slide over sharp, square target can leave you a NASTY gash across your palm. Don't ask me how I know.
*In this context, "BoMar" and "Novak" are generic terms, not brand names.