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This product is called the MBUS (Magpul® Back-Up Sight), which is a folding back-up sight. It's affordable and made from color injection-molded materials. The front sight is adjustable for elevation, and it can fit most 1913 Picatinny-railed hand guards but is designed specifically for the AR15/M16 platform. The package includes an elevation adjustment tool, but it's also compatible with most aftermarket A2 front sight adjustment tools. This product is made in the USA.

One of the significant advantages of this product is its spring-loaded flip-up sight, which can be activated from either side or by pressing the top. Additionally, protective wings shield the spring-locking A2 front sight post. The polymer construction provides light weight and resists operational abuse. The detent and spring pressure keep the sight erect while allowing for unobstructed folding under impact.

This product is compatible with most MIL-STD-1913 Picatinny / STANAG 4694-railed hand guards and delivers the same height-over-bore as standard A2 irons. The front sight has a length of 1.5 inches when deployed and 2.6 inches when stowed, with a weight of 1.2 oz including hardware. The elevation adjustment is ~1.6 MOA (1.886"/100m) per click with a 14.5" sight radius and ~1.2 MOA (1.367"/100m) per click with a 20" sight radius.

One thing to note is that this product cannot be mounted to a railed gas block due to excess heat issues. The front MBUS must be mounted to a railed fore end on the same plane as the receiver rail, making it incompatible with MOE Hand Guards.

In conclusion, the MBUS is a reliable and cost-effective folding back-up sight that offers many advantages. It has a spring-loaded flip-up sight and protective wings that shield the spring-locking A2 front sight post. Made from impact-resistant polymer, it provides light weight, resists operational stress, and maintains sight erectness. Additionally, it's compatible with most MIL-STD-1913 Picatinny / STANAG 4694-railed hand guards, providing the same height-over-bore as standard A2 irons, and comes with an elevation adjustment tool. All of these features make the MBUS stand out from competitors on the market.