The Magpul MBUS Rear is a folding polymer dual-aperture back-up iron sight for AR-15 and M4 rifles, clamping to any MIL-STD-1913 Picatinny rail.
The Magpul MBUS (Back-Up Sight, MAG248) rear folds flat to clear your optic and flips up instantly when you need irons. It gives you the familiar dual-aperture setup — a large aperture for close, fast work and a small aperture for precision — with tool-free windage adjustment via a positive-click knob. The impact-resistant polymer body sheds knocks and weight in equal measure.
Run it with the MBUS front for a complete, dependable backup iron sight system on any optic-equipped carbine.
How It Compares
This original MBUS is the light polymer option. The MBUS 3 Rear Sight is the updated generation, and the MBUS Pro Rear Folding Sight is the all-steel version with a slimmer folded profile.
Key Features
- Dual apertures: fast close-range and precise long-range settings
- Tool-free windage: positive-click adjustment knob
- Spring-assisted deployment: flips up positively at a button push
- Impact-resistant polymer: tough, light, corrosion-proof
- Four finishes: Black, Flat Dark Earth, Stealth Gray, Olive Drab Green
Compatibility & Fitment
Clamps to any MIL-STD-1913 Picatinny rail on a flat-top AR-15/M4 upper. You need clear rail behind your optic or mount, and the front and rear should sit on the same rail plane. Pair it with the MBUS front (MAG247) to complete the set, then zero windage on the rear and elevation on the front.
What's Included
- Magpul MBUS rear sight
- Integral rail clamp and cross-bolt
Technical Specifications
Platform | AR-15 / M4 |
Type | Folding back-up rear sight (BUIS) |
Material | Impact-resistant polymer |
Finish | Black, Flat Dark Earth, Stealth Gray, Olive Drab Green |
Mount Interface | Picatinny / MIL-STD-1913 |
Adjustment | Windage (tool-free), dual aperture |
US Shipping & Support
Shipped from D&R Sports Center in the USA with fast, tracked delivery. Questions on fit, mounting or which model suits your setup? Our team is glad to help before and after your purchase.
Frequently Asked Questions
Will the MBUS Rear fit my rifle?
It clamps to any MIL-STD-1913 Picatinny rail on a flat-top AR-15/M4 upper. You need clear rail behind your optic or mount for it to sit on, and the front and rear sights should end up on the same rail plane so the sight picture lines up. If your optic mount takes up the whole rear rail, move it forward or choose a mount that leaves room.
What do the dual apertures give me?
You get the familiar two-aperture arrangement — a large aperture for close, fast work where speed matters more than precision, and a small aperture for more deliberate shooting at distance. You flip between them rather than adjusting anything. Windage is set on a positive-click knob that needs no tools, so you can correct a zero on the range without carrying anything extra.
How does it compare with the MBUS 3 and the MBUS Pro?
This original MBUS is the light polymer option and the most affordable way to put a folding rear on a carbine. The MBUS 3 is the updated generation, and the MBUS Pro is the all-steel version with a slimmer folded profile. If you want elevation adjustment on the rear as well, the MBUS Pro LR adds it.
Is fitting and zeroing straightforward?
Yes — the rail clamp and cross-bolt are integral, so it slides on to the rail where you want it and the cross-bolt tightens it down. Pair it with the MBUS front (MAG247) to complete the set, then zero windage on this rear sight and elevation on the front post. The windage knob is tool-free, so no armorer's kit is needed.
