Best Backup Iron Sights (BUIS) [Ultimate Guide 2021]

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In this guide I’m going to show you the best backup iron sights.

In fact:

These are the same sights that many scope experts and competitive shooters use.

The best part?

I’ve sorted the sights by use. So whether you’re on a budget or need a solid AR-15 iron sight, you’ll find it here.

Let’s get started!

The 4 Best Backup Iron Sights

If you’re pressed on time, here’s a quick list of the best backup iron sights:

  1. Magpul MBUS PRO Steel: Best Overall BUIS
  2. Troy Industries Micro HK Style: Best for Low-light Shooting
  3. Magpul MBUS Front & Rear Flip Up GEN 2: Best Flip Up Sight for AR-15
  4. Daniel Defense A1.5 Fixed Rear Sight Assembly: Best Rear Sight for AR-15

1. Magpul MBUS PRO Steel: Best Overall BUIS

Do you want the best low profile backup sights for your AR platform?

Then take a hard look at Magpul’s MBUS PRO Steel.

It’s honestly one of the toughest backup sights on the market. Here’s what I like about the MBUS PRO…

Durability & Size

The all-steel construction of the MBUS PRO makes it one of the toughest backup sights on the market.

I love steel, and short of the sights being welded directly to your receiver and barrel these tough Picatinny mounted sights are about the strongest setup one could hope for in flip up sights.

Not to mention that Magpul has kept the whole setup just 3.4 ounces, so you aren’t adding a lot of extra weight, something everyone starts to think about after adding a heavy scope or red-dot to their otherwise lightweight AR setup.

Mounting & Installation

No need for separate scope mounts or riser sections, and installation is as easy as turning a screwdriver.

In my opinion, a dab of blue Loctite helps to hold everything securely. When I mount back-up sights, I sort of want them to stay put…forever.

Loctite 487229 Threadlocker 242 All-Purpose Medium Strength Tube, Blue, 6 ml
  • DESIGN. Ideal for fasteners under 1/4-Inches to 3/4-inches (6 mm to 20 mm).
  • RESULTS. Secure, one-piece assembly that will not loosen under stress.
  • SECURE. Locks and seals while preventing parts from loosening due to vibration.

The ring height is 1.41 inches, which is a touch shy of the 1.5 centerline of a red-dot sight, which placed the tip of the front post directly under a 2-4MOA dot. In other words, these are quite perfect for a typical co-witness setup.


No special tools required to adjust the elevation or windage with manual flip up.

That’s right, no need to get the special detent tool in order to adjust your sight. This is great for me because I have never been able to keep track of a tool, so I end up pressing those annoying detents on most of my setups with a tiny screwdriver or the point of my knife.

The Magpul sights have sturdy 0.5MOA clicks that stay put, so they are always on when you flip them back up, with no need to adjust them further.

The manual flip-up isn’t as cool as a spring-loaded button that you see on other sights, but it’s also one less moving part that can break or flex when you need it the most.

Sight Style and Size

Two front post options are included, and there is a selectable rear aperture, which makes these sights useful for both target competitions and typical field conditions.

My personal choice is to install the narrower front post before even installing these sights on my rifle and leaving the target peep down, which provides a clear sight picture with pretty decent accuracy.

The 0.19 inch rear aperture in my opinion is a must, while the .07 flip up insert is nice to have at the range or when sighting in the rifle, but otherwise I could do without it. It’s simply too easy to blur the sight picture in low light and slow to acquire at close range, defeating one purpose of iron sights.

To each their own.


The one downside to this sighting system is the price.

They are nearly twice the cost of other iron back-ups, but if the features match your wish list, you won’t find a better quality system out there.

  • All-steel construction
  • Perfect co-witness height
  • Variable sight picture dimensions
  • Strong detent adjustment with no tools
  • Positive feedback when folded or deployed

If you can afford them, the Magpul MBUS PRO Steel sights are the most solid irons on the market to add to your AR rail.

Magpul MBUS PRO Steel Sight Set MAG275 & MAG276 Black
  • Melonite Finish;Windage adjustable with low-profile knob
  • Made from Steel (NOT POLYMER)
  • Front Sight can be mounted on Railed Gas Block

2. Troy Industries Micro HK Style: Best for Low-light Shooting

If you’re looking for the best iron sights for low-light shooting, the Troy Industries Micro HK Style fit the bill.

They’re ruggedly durable and made for weapons with a raised top rail system.

I put these on my H&K 416 and have never looked back.

Want to know why? Keep reading…

Durability & Size

Troy Industries is a brand you can trust when it comes to durability and these sights are high quality.

They’re made of solid steel and well-machined.

They feel solid and sturdy and can definitely take a beating.

The Troy Industries Micro HK Style are low-profile, which is why they’re perfect for weapons with a raised top rail. They won’t get in your way.

They’re also great for anyone that just wants a sight picture closer to the barrel.

Mounting & Installation

Mounting and installing these sights was quick and easy.

The only problem is that you need to buy an extra tool to do it. Or at least to get the sights adjusted properly.

Luckily, the Troy Industries Battle Sight adjustment tool is cheap. And, it gets these sights to perform optimally.

Troy Industries Battle Sight Adjustment Tool
  • Easily adjust elevation
  • Adjust windage
  • Troy Industries

Once you get these on, they fit tightly and don’t wiggle at all. And mine were dead on!

Special Features

These sights have a couple features that make them really great.

The low profile makes them easy to co-witness with a red dot sight, without even needing a riser!

Plus, they are the perfect BUIS for any rifle scope because they flip up and fold down, so they’re there when you need them and out of the way when you don’t.

On top of that, these sights also feature the HK style, which means that the front sight is rounded and kind of looks like wings.

What I like about that is that they’re much faster and easier to line up than a traditional sight. Especially in low-light conditions. They’re really easy to spot. At least, they are for me.

Are the Troy Industries Micro HK Style sights worth it?

These iron sights are well worth the cost for low-light or really any light conditions.

They feature:

  • Tight fit
  • Low profile
  • Rugged durability
  • Flip up capabilities
  • HK style, rounded front sight

If you want iron sights that make the best BUIS or just need something for a raised top rail system, try the Troy Industries Micro HK style sights. You’ll be happy you did.

Troy Industries Micro HK Style Front and Rear Folding Battle Sight
  • Rugged low-profile sight
  • Enhances weapons, with raised top rails
  • Black

3. Magpul MBUS Front & Rear Flip Up GEN 2: Best Flip Up Sight for AR-15

If you’re like me, then you spent a lot of time and effort making sure you got the perfect optic for your AR-15.

Well, I’m here to tell you that you should really spend that same effort when it comes to your backup sights. You don’t want to be left with nothing if your primary scope fails.

Lucky for you, I’ve already done the hard part. I’ve researched and tested dozens of backup irons, and I’m here to tell you that by far, the Magpul MBUS Gen 2 is the best flip up sight for the AR-15 platform.

But you don’t have to just take my word for it. Let’s look at the evidence.

Visibility and Accuracy

First off, let me say that the Gen 2 MBUS sights are easy to use and accurate.

The rear ring draws my eye in to center quickly, and the front post allows me to precisely place rounds downrange.

There are even two apertures to choose from. The rear aperture is actually split into both Target and Combat apertures. The Target aperture is narrower and allows for precise shooting. But with a simple flip down on the aperture, it opens up to the Combat setting which allows for a wider field of view and speeds up your target acquisition.

Talk about versatility!

And these things are spot-on accurate, too. I was able to zero in these sights using the included sight adjustment tool within a handful of rounds and they’ve held their zero perfectly through months of testing, hundreds of rounds, and countless flips up and down.


Don’t be thrown off by the fact that the MBUS AR-15 sights aren’t all-metal: the polymer construction is a feature, not a bug.

See, this isn’t some cheap plastic. It’s a high quality, impact resistant polymer that can actually withstand more abuse than metal sights. Plus, the polymer weighs less than traditional all-metal ironsights. The whole set only weighs 2.5 ounces!

The springs that allow for the flip operation are sturdy and provide a lot of tension.

They keep the sights up when you need them, but will also allow the sights to flip back down if you accidentally drop your rifle on them. This keeps them from snapping or bending, and should help ensure a lifetime of solid operation.

plus, there are these handy little “wings” built into the sides of the sights that shield the front post and rear aperture from any accidental impacts.

And, if all that wasn’t enough, the MBUS sights are completely made in America.


Installation of the Magpul Gen 2’s onto any picatinny rail is quick and simple. You’ll only need a flathead screwdriver.

First, as always, make sure your weapon is completely unloaded, chamber emptied, and safetied!

The MBUS uses a through-bolt to lock it into place. Unscrew the bolt from the sight, while making sure not to lose the nut on the other side. Then slide the front sight over the front of your AR’s picatinny rail. Once you have it where you want it, slide the bolt through the side of the sight. It should slot into your picatinny rail. Then, holding the nut in place on the left side, tighten the bolt with your screwdriver.

To mount the rear sight, you’ll first need to pull back the bolt and charging handle of your AR15 so that you can access the back of the rail. Then, just repeat the same process you just used for the front sight, and bam, you’re good to go!

I like to keep my rear sight as far back as possible, and my front sight as far forward as possible. This way I have plenty of space to mount my primary optics and any other accessories on my AR15.

And, since the Magpul sights sit at the same height as standard A2 irons, they work perfectly as co witness sights for my Vortex Strike Eagle.

Flip Operation

Flipping the MBUS Gen 2’s into place is a cinch.

There are levers on both sides of the sights, so you can operate them with either your left or right hand. You can even press on the top to deploy the sights, if you’d prefer!

To fold them back down, simply press them back into place until the lock in.

Like I said, I’ve deployed and stowed these sights more times than I can count. And the springs and locking mechanisms are all still solid.

The Verdict

When it comes down to it, a good set of backup sights is just as important as a good riflescope.

That’s why I recommend the Magpul Gen 2 flip up sights.

They’ve got:

  • Low weight
  • Solid durability
  • Easy installation
  • Easy ambidextrous operation
  • Target and Combat rear apertures

So if you’re looking for a solid, high-quality set of flip up iron sights for your AR15, look no further than the Magpul MBUS Gen 2 Flip Up Sights.

Looking for a good red dot sight for your pistol? Check out this list of the top choices.

4. Daniel Defense A1.5 Fixed Rear Sight Assembly: Best Rear Sight for AR-15

Sometimes a set of folding back-up sights just don’t cut it. If you are looking for a full-service, fixed rear sight, Daniel Defense has just what you need.

Daniel Defense is well known for building some of the best AR15 components and accessories. Their A1.5 fixed rear sight assembly is dependable and will fully co-witness with your reflexive optic.

Let’s take a look…

Durability & Size

The Daniel Defense A1.5 Fixed Rear Sight Assembly is made from machined 6061 aircraft grade aluminum. Not only is it light weight, it’s tough too.

It features a hard anodized finish that won’t scuff or corrode over time. This sight–like everything else Daniel Defense makes–is built to last.

The sight is about 1 inch long by 1 inch wide by 1 inch high. It doesn’t have an excessive footprint on my rail. And it weighs less than 2 ounces. Honestly, I can hardly tell that it’s there.

It doesn’t interfere with my charging handle. And it will match perfectly with any standard size M4 front sight that you have.

Mounting & Installation

The Daniel Defense A1.5 Fixed Rear Sight Assembly uses a special screw that twists right into my rail.

It was easy to put on and once attached won’t go anywhere. That thing solidly mounted to my rifle. I couldn’t scrape it, beat it, or pry it off if I wanted. Trust me–I’ve tried.

Setting Zero

Once my optic was mounted, I needed to sight it in or find zero. That means I needed to make the point of impact align with my point of aim.

The sight has adjustable windage. I couldn’t use just my fingers to make adjustments. There’s a little metal ball that locks the adjustment wheel. This is a great feature because I can’t accidentally knock my rear sight out of alignment.

That little metal ball needs to be intentionally pressed down to adjust my windage.

While the rear sight doesn’t come with a special tool to make the adjustments, I could easily move it a click or two using a spent round casing.

I just needed to use the edge of the casing to depress the metal ball in the middle and then I could spin the dial. It was really easy to do.

A fine pointed punch press would work well too. However, I found using a spent casing really convenient to use at the range when I was sighting this in.

The optic was easy to zero. It took a few shots to walk the windage into bullseye. I did need to adjust my elevation a click, and to do that, I needed to adjust my front sight.

Overall, finding zero was easy and once it was set, I know it will hold forever. This rear sight by Daniel Defense isn’t going anywhere.

Special Features

The Daniel Defense A1.5 Fixed Rear Sight Assembly has a through cut design that cuts weight and makes for one sleek iron sight. It’s unobtrusive and doesn’t interfere with the reflexive optic I have mounted.

I can hardly tell it’s there. But I can depend on it when I need it.


The Daniel Defense A1.5 Fixed Rear Sight Assembly is awesome. Don’t let its modest appearance fool you. This rear iron sight is well designed and full of features:

Daniel Defense A1.5 Fixed Rear Sight Assembly - 19-064-11002,Black
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Daniel Defense A1.5 Fixed Rear Sight Assembly - 19-064-11002,Black
  • Package length: 13.97 cm
  • Package width: 7.62 cm
  • Package height: 6.35 cm
  • Easy to mount
  • Simple to zero
  • Locking windage
  • Sturdy aluminum design

I can recommend the A1.5 Rear Sight Assembly to anyone who is looking for a dependable fixed sight. I am very comfortable betting my life of its durability and functionality. You can’t go wrong with Daniel Defense.

If you are in the market for a budget optic, check out this list.

Or if you need an extra durable scope for your muzzleloader, these are great.

Now It’s Your Turn

I hope you enjoyed my best backup iron sights guide.

Now I want to turn it over to you:

Which sight will you pick for your firearm?

Let me know by leaving a quick comment down below.

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