Best Backup Iron Sights (BUIS) [2019]

Back in the day, you’d know who was a crack shot through their use of iron sights.  

These days, that’s not as much of a problem for the average shooter.  Unless you’re running through 3-gun competitions or you’re a traditionalist, you’ve probably considered mounting an optic on your gun if you haven’t already.

If you’re interested in why we like these BUIS, you’ll need to read on. But if you just need to know what we like – here you go:

Polymer Means Light WeightMagpul MBUS
Alternative PolymerFab Defense Flip-Up
Best All MetalTroy Micro MBUIS
Low-Profile Bobro Lowrider BUIS
45 Degree OffsetKAC 45-Degree Folding Micro Sight
BUIS mounted on Pickatinny rail
BUIS mounted on Picatinny rail

We now live in an era where red-dots, ACOGs, holographic sights, and lasers are not only readily available, they’re also affordable.  But what happens when the batteries on your red-dot die or your holographic took one fall too many and aren’t working as well as it should?  This is where backup iron sights (BUIS) become worth their weight in gold.

Whether your gun is used for hunting or self-defense purposes, if you’ve got optics mounted on it, you should also have BUIS in the event of a sight malfunction.

Today, we’re going to look at some reliable BUIS to use when you’re in a pickle.

Magpul MBUS

The Magpul Back-up Sight, aka MBUS, is an affordable sighting system that is designed for the AR-15 platform.  It’s an affordable and effective back-up to your optical sighting system.

Magpul’s front and rear sights are both built with a lightweight and durable polymer that’s can handle any wear and tear you throw at it without any major issues.  As long as you’ve got a Picatinny rail system on your gun, you’ll have no problem mounting these BUIS in minutes.

Both sights are capable of folding down, so you don’t have to worry about them being in your way when they’re not in use.  The internal spring system built into the MBUS helps make the sights sturdy enough to withstand bumps and knocks without unintentionally folding down.

Since the MBUS are the same height as the A2 sights, you don’t have to worry about getting used to a new pair of sights.  And if you want to make any adjustments, the rear sight has an easy-to-use knob for adjusting windage, while the front sight comes with a tool for making changes to the elevation.

What’s your take on the the MBUS?

Readers' Ratings

4.97/5 (186)

Your Rating?

FAB Defense Flip-Up Sights

Straight from the guys that make stuff for the Israeli Defense Forces comes the FAB Defense Flip-Up Sights.

67 at Amazon

Prices accurate at time of writing

Lightweight like Magpul’s but doesn’t have the internal spring system.  Which can be good or bad depending on your situation.

Fab Defense BUIS, Down
Fab Defense BUIS, Down

If it’s rare to deploy your BUIS…I actually like FAB’s system since you don’t unintentionally activate the front sight if you use a far-reaching c-clamp grip.

View-through is great and sight is easily adjustable too.

Fab Defense BUIS View
Fab Defense BUIS View

Troy Micro HK-Style Front and Rear Sights

If you’re looking for something that’s sturdy and dependable, Troy Micro HK-Style MBUIS are strong enough to take a lickin’ and keep on tickin’.  These low-profile iron sights are under 1.5” in length and only weigh a couple of ounces, meaning that they’re conveniently out of the way until needed.

Because of their low-profile design, the Micro BUIS could require a bit of adjusting when mounted on your M4.  But if you’re running a raised top rail system then the Micros are great to shoot with.  Troy recommends mounting them to the Sig Sauer 556 carbine and the FN Scar.

198 at Brownells

Prices accurate at time of writing

Overall, the Micro BUIS are pretty cool.  They clamp easily to your Picatinny rail system where they remain folded down until you need to put them to work.  You can also flip the rear sight aperture to choose between short/medium-distance and long-distance (300 – 600 yards) shooting.

The best feature of the Micro BUIS is its rugged design.  This makes it an excellent alternative for anyone who’s not so keen on the polymer sights and wants something actually made out of metal – as the name iron sight implies.  In addition, the tritium really helps to make the sights visible, which is perfect for low-light shooting.

A.R.M.S. Inc. #40 L-F Combo

The #40 front ($130) and rear sights ($135) are a reliable set of BUIS that will make sure that your AR-15 doesn’t lose accuracy in the event of an optical mount getting banged up or malfunctioning.  Their low-profile design makes them excellent for your flat-top due to the fact that they take up very little space and can be folded down when not in use.

130 at Brownells

Prices accurate at time of writing

Like a lot of other BUIS for the AR-15 platform, the #40 rear sight comes with a flip-adjusted aperture that switches between short and long-range shooting.  Also, unlike some of the other BUIS out there like the MBUS, the front sight of the #40 can be mounted to the gas block without any issues.

One of the more popular features of the #40L-F is its lower-than-usual profile which gives the shooter far more clearance when mounting an optic to their AR-15.  Also, to avoid unnecessary damage to the front sight, A.R.M.S. designed the sight to fold back when struck from a front angle.  That’s definitely a plus for those of us who are a little too rough with our guns.

Bobro Lowrider BUIS

The Lowrider BUIS set by Bobro ($199) might not be cheap, but it’s a solid set of BUIS to have for anyone looking to conserve space on their AR-15.  So, if you want a set of dependable flip-up sights while also having enough room for your lasers, lights, and other mounts, then the Lowrider BUIS is an excellent choice – especially for shooters with short-barreled rifles.

200 at Brownells

Prices accurate at time of writing

With the Lowrider sights, you don’t have to worry about your rear sight getting in the way and interfering with your other accessories.  And just like most other BUIS out there on the market, the Lowrider is able to be fully adjusted to compensate for elevation and windage, and they’re able to be locked flat into place when flipped down.

Another benefit of the Lowrider sights is the infinite adjustment instead of clicks-based adjustments, a common feature with other quality BUIS out there.  This makes it easier for Lowrider BUIS to be mounted in compact and full-sized rifles without any issues with aiming.

Overall, the Lowrider sights are sturdy, lightweight, and are excellent at what they do.  With that said, there’s only one aperture in the rear sight and neither the front or rear sight is able to lock into place when flipped up.

KAC 45-Degree Offset Folding Micro Sight Kit

If you’ve got no problem dropping a lot of money on a set of BUIS, the folding micro sight kit by KAC ($284) is arguably the Cadillac of iron sights.

But what makes a BUIS so special that it costs the same amount as a red-dot sight?

For starters, KAC’s sights are some of the easiest to adjust on the fly.  Instead of having to use special tools, the shooter can change elevation and windage with their hands.  All you need to do is turn the specific knob in the direction that you’d like the sight to be adjusted to.

285 at Brownells

Prices accurate at time of writing

The other major benefit of the 45-degree angle BUIS is the way they’re designed to not interfere with all other optics mounted to your device.  Whether you want to take a quick shot without a scope or your red-dot just died out, you’re able to easily squeeze off a round with the 45-degree sight by giving your rifle a slight counter-clockwise rotation.

While that may sound strange and even unnatural, it’s shooting with the 45-degree sights is actually easy – even intuitive.  Have a look at this quick video to see how they’re put into action.

The final word on KAC’s Offset sights is that they’re great to have, provide you’re willing to spend the money.  But the fact that they’re compact, lightweight, and never get in the way makes them completely worth it, especially if you’re shooting with a scope.

However, there is one drawback to the sights: the aperture.  Instead of being able to cycle through apertures like you could with other KAC sights, the 45-degree offset comes in two versions: the 300-meter and the 200 – 600-meter version.  So make sure you choose wisely before spending so much money.

Ade Advanced Optics Offset Sights

Don’t have the coin for KAC?  Check out the ultra-affordable AAO Offset Sights ($24) that have awesome reviews.

22 at Amazon

Prices accurate at time of writing

We also have even more at Best AR-15 Offset Sights.

But Do I Really Need Back-Up Iron Sights?

I get it, redundancy isn’t a good look.  You don’t want to be that person who has every single gadget known to man mounted on their AR-15.  It’s bulky, unnecessary, and cumbersome.

Rear sight
Rear Sight

The thing is, BUIS should be neither redundant nor cumbersome.  And if they are then you’re probably doing it wrong.

The AR-15 market has come a long way from its older detachable carry-handle design– and we all remember how unnatural the 3x optical scopes felt mounted to those.  

As you already know, AR-15s are now designed optical-ready and built with rail systems.  

Because of this, a number of manufacturers have begun making ARs without iron sights.  After all, most people rush out to buy a red-dot sight anyway.  And whether companies do this to cut back on manufacturing costs or because the average shooter prefers mounting their own sights is irrelevant.

Mounted rear sight
Mounted rear sight

Back to whether you actually need BUIS or not – the answer is unequivocal yes, you do need them.  The last thing you want to happen if your red-dot or holographic goes haywire is to be shooting blind.  Fortunately, BUIS are easy to mount and are available for pretty much every kind of budget, so you’re always able to have a Plan B.

You can even get 45-degree mounts like the KAC mount up above in order to have iron sights mounted to the side of your primary optic for quick, up-close shooting.

Now that we’ve covered the importance of BUIS and looked at some good ones on the market, you’re ready to upgrade your AR-15.  Also, don’t forget to check out our extensive red-dot guide while you’re shopping around for optics.

Do you have BUIS on your rifle?  If not, did any of these catch your eye? Let us know in the comments below.

Leave a Reply

9 Comment threads
4 Thread replies
Most reacted comment
Hottest comment thread
13 Comment authors
napior1985David, PPT Editornumb1jeepguyAiden H.Angel Recent comment authors
newest oldest most voted
Notify of

Hi, Thanks for valuable staff.

Have you tried ERATAC ?


What brand is the rear flip up in the very last photo of the article?

David, PPT Editor

I prefer the LWRC skirmish sights. I like that you can turn the back sight around , as opposed to flipping it up and down. The allows you to choose either short or long distance from the rear sight aperture when the rear aperture is folded flat. I’m not sure if they have a patent on this or not. It seems like such an easy thing to do, I don’t know why other manufacturers haven’t copied this.

Terry L Belden
Terry L Belden

My ar came without sights, I put a red dot on it, but am ready to toss it and put iron sights on. What do you recommend for a front sight. I do not have a very long rail so it would need to be barrel mount.


Magpul makes an outstanding set of 45 degree offset BUIS. They’re fully adjustable by hand, solid steel construction, fold down for an extremely low profile, and less than $200. I absolutely love them.

New to Guns ? Check out our beginners guns video course. Start Now