The FN, Glock, and S&W all came from the factory with a cover plate attached to the top of the slide just forward of the rear sight. A hex wrench was used to remove the plate and replace it with a mounting plate the corresponded to a specific model and brand of reflex sight. All three manufacturers include the tools to mount the sights, and as we found out, some provided more mounting options than others. All the hardware types mount the sight slightly differently, as we will explain. Mounting the sight allows the user to also keep the iron sights mounted on the slide, and the FN and S&W featured taller iron sights that cowitnessed with the red dot. The Glock's sights were standard size and could not be used when a red dot was attached, so if the shooter wanted to co-witness (shoot to the same point of impact) iron sights with the red dot, he would have to install taller Glock sights like those used with a suppressor, which would appear in the reflex sight window. Mounting the optics was straight forward.