So my friend bought a primary arms reflex sight in hopes of mounting it on his FN 5.7 pistol. He did not realize that there needed to be mounting system. I told him I would ask around see if anybody had an idea. The sight has a built in weaver mount. So I guess what I am looking for is a type of rear sight that is dove tail on the bottom and a weaver rail on top. I dont have access to the pistol so i cant measure the actual width of the dove tail. Anybody have an idea? Any help would be greatly appreciated. Thank you gentlemen.