Mbus pro - the go-to standard for rail-mounted sights - Magpul Industries MBUS Pro Flip Up Sights

This is the second set of the Magpul MBUS Pro flip Up sights I have purchased. While Magpul makes polymer versions of this sight at about half the price of the Pro series, the steel construction of the Pro model is much superior in ruggedness and durability - you'd be hard-pressed to damage an MBUS Pro sight beyond functionality, short of beating it with a sledge hammer. Absolutely the best military-grade rail-mounted sight out there. An added feature is the adjustable sight post: there is a "fat" (wider) profile for general use, and a thin profile for precision targeting - you can go from one to the other with a click, no tools needed. The sight locks up or down and is firmly engaged in either position; in the down position, its profile is minimal - ideal if you're running an optic. While pricey compared to the polymer versions, you get what you pay for - basically a near-indestructible sight that you can count on when the SHTF. I highly recommend this sight - bolt it on and forget about it - it'll be there when you need it.