Meprolight ML31615F.S 31615FS / ML31615FS: Meprolight Tru-Dot night sights feature unequaled low-light performance as the brightest night sights available. This model features self-illuminated green Tritium front sight only for use on AR-style A1 and A2 rifles. It has a round front post, which is much narrower than the square post currently coming on the AR rifles. This thinner post gives more accuracy since it does not cover as great an area of the target at distances. This model is two-piece for alignment. Front sight only.