Magpul MBUS Flip-Up Rear Backup Sight, Black — Polymer, Dual-Aperture, Picatinny Clamp

Magpul MBUS Flip-Up Rear Sight in black is a lightweight, spring-loaded backup iron sight engineered to clip to MIL-STD-1913 Picatinny rails and provide reliable windage adjustment when optical systems fail.

Designed and manufactured in the USA, the MBUS rear sight is a cost-effective polymer folding backup that pairs with Magpul front MBUS sights or other A2-height front sights to deliver an immediate, low-profile aiming option. Its color-injection molded construction resists impact and operational wear, while the spring-detent mechanism keeps the sight upright during use yet allows unobstructed folding when stowed or struck. The dual-aperture rear offers both precision and speed for short- and mid-range engagement geometry.

How does the MBUS Rear Sight perform as a backup on a loaded rifle?

The sight uses a robust detent and spring system so it stays erect during handling and recoil but folds flat if impacted to avoid damage. The dual-aperture design gives a small, precise peep for accuracy and a larger aperture for quicker target acquisition under stress.

• Detent and spring pressure retain upright position without tools
• Dual apertures for precision or rapid aiming
• Protective wings shield the sight post from knocks and debris
• Provides standard A2 height-over-bore when paired with compatible front sights

How simple is installation and zeroing of the Magpul MBUS Rear Sight?

Installation clamps directly to most Picatinny/MIL-STD-1913 rails and secures with a captive cross-bolt clamp, requiring only basic hand tools. Windage is adjustable with a quick-turn mechanism so you can dial the rear aperture left or right to align with your front sight during zeroing.

• Clamps to MIL-STD-1913 / STANAG 4694 rails without gunsmithing
• Tool-friendly windage adjustment lets you center the aperture precisely
• Same height-over-bore as standard A2 iron sights for compatibility
• Can be paired and indexed easily with Magpul MBUS front sights

Will this rear sight stand up to field conditions and rough handling?

The MBUS rear sight uses impact-resistant polymer and a spring-loaded flip-up mechanism engineered to tolerate heavy use, drops, and environmental exposure. The injection-molded construction resists chips and corrosion common to metal parts, while the spring and detent design allow the sight to fold unobstructed if subjected to sudden impact.

• Impact-resistant polymer reduces weight and resists operational abuse
• Spring-loaded flip-up action activates from either side or the top
• Folds cleanly under impact to avoid damaging the aperture
• Made in the USA to Magpul quality standards

What accessories and compatibility should I consider before buying?

The MBUS rear sight pairs with most standard A2-height front sights and aftermarket adjustment tools, and it works on any Picatinny/STANAG 4694 rail geometry. Magpul includes an elevation adjustment tool for the front sight, while the rear sight’s windage is adjustable without specialized gear.

• Compatible with most A2-height front sights and MBUS front units
• Works on MIL-STD-1913 and STANAG 4694 rails out of the box
• Elevation adjustment tool included for the front sight, rear adjusts for windage
• Lightweight profile keeps sight radius and balance predictable

Who is this for: The Magpul MBUS Flip-Up Rear Sight is ideal for shooters who want a dependable, low-cost backup iron sight that won’t add significant weight or bulk. It’s well suited to tactical users, hunters, law enforcement, and recreational shooters who mount optics but want an immediate, rugged fallback solution. If you need a compact, weather-resistant rear sight that installs quickly on a Picatinny rail and pairs with standard A2-height front sights, the MBUS rear sight delivers practical performance and proven durability.