The Reflex Sight is an attachment used to increase accuracy. It has a crosshair-style reticle, as well as a wide viewing range within the sight. This does not provide any magnification, although it does improve accuracy. This sight is recommended for use on guns that are effective at short range, such as the M1014 and M870, although secondary submachine guns like the CBJ-MS and Uzi are useful with it too.
While this is regarded as one of the most useless sights in the game by many snipers and people who prefer medium range, this is much much better than any of the iron sights in game.