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Best Backup Iron Sights (BUIS) [View-Throughs]

Optics break, batteries die, and scopes fail. A pair of these backup iron sights (BUIS) will make sure you have working sights at all times.

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.

Fighting Rifle BUIS
BUIS

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 they should?

This is where backup iron sights (BUIS) become worth their weight in gold.

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

Summary of Our Top Picks

  1. Affordable Option

    Magpul MBUS

    Reliable, durable, and budget friendly.

  2. Lightweight Option

    FAB Defense Flip-Up Sights

    Lightweight and easy to adjust.

  3. Low-Profile Option

    Troy Micro BUIS

    Low profile, clamps easily to Picatinny rails.

  4. Durable Option

    A.R.M.S #40 BUIS

    Durable and reliable.

  5. Offset Option

    KAC 45 Degree Offset BUIS

    Easy to adjust on the fly, 45-degree angle

  6. Affordable Offset Option

    AAO Offset BUIS

    Budget-friendly offset

Best AR-15 BUIS

1. 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 backup to your optical sighting system.

Affordable Option
37
at OpticsPlanet

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

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.

Magpul MBUS Rear Sight
Magpul MBUS Rear Sight folded down

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 MBUS? Give it a rating below.

Readers' Ratings

4.89/5 (909)

Your Rating?

2. FAB Defense Flip-Up Sights

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

Lightweight Option
79
at Amazon

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

Lightweight like Magpul’s but doesn’t have an 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

3. 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 inches 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.

Low-Profile Option
209
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

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 to 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.

4. 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.

Durable Option
130
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

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.

5. 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.

Offset Option
285
at Brownells

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

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, shooting with 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 to 600-meter version. So make sure you choose wisely before spending so much money.

6. Ade Advanced Optics Offset Sights

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

We’ve been testing them out for competitions where we leave our 1-6x scopes at magnification and use these bad-boys for quick and dirty close-up shots.

Ade Advanced 45 Degree BUIS
Ade Advanced 45 Degree BUIS

Here they are mounted on one of our rifles.

Ade BUIS on LWRCI AR
Ade BUIS on LWRCI AR

And of course…how they actually look.

Viewthrough of Ade 45 Degree BUIS
View through of Ade 45 Degree BUIS

It’s up to you to decide if that’s worth it…but for quick man-sized target shots up to 25 yards…I love them.

Affordable Offset Option
18
at Amazon

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

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 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.

A Couple AR-15 Optics
A Couple AR-15 Optics

Do you have BUIS on your rifle?  If not, did any of these catch your eye? Let us know in the comments below. Want go to electronic? Check out our Best AR-15 Scopes & Optics. To get the lowdown on how to zero irons, check out our guide!

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24 Leave a Reply

  • Commenter Avatar
    Phil S.

    I’m pretty happy with my Griffin Armament M2 sights. The same sights can be purchased with 12 o’clock base, 45 offset base, or both bases. I have them set up as 45 offset because I don’t have a quick release mount for my optic.

    March 6, 2022 4:23 pm
  • Commenter Avatar
    Michael W. Clemons

    It's all junk. Learn to shoot irons and free you gun up. At least then you will be able to see if there's a gun under all that crap.

    February 2, 2022 11:07 am
  • Commenter Avatar
    Michael W. Clemons

    No junk on my AR. Some of those outfits you can't be sure there is a rifle under all the bull*hit.

    February 2, 2022 11:06 am
  • Commenter Avatar
    Natonia Clemons

    Sometimes I look at all the junk stuck on the AR's and ask myself 'Is there a rifle under there?'

    February 2, 2022 11:05 am
  • Commenter Avatar
    Travis Thams

    Dude. You realize the ADE offset sights are designed for airsoft right??? They’re for TOY RIFLES! Not a weapon you depend on to save your life.

    October 3, 2021 10:38 pm
  • Commenter Avatar
    adam

    Magpul BUIS links to a knock off copy. Be warned.

    June 9, 2021 4:34 pm
  • Commenter Avatar
    James

    Wow, you really don't give Patriot Ordnance Factory ANY respect. Frank DeSomma worked with Diamondback to produce a "low rise" version of their standard height model, called the Micro-D.
    The Diamondback rear sights have three positions, ghost ring (for CQB/CQC), large aperture (for mid-distance), and small aperture (for long distance).
    Diamondback ALSO has a multi-post front sight option, where the rotating selector has several different size posts, select the post that matches the height of the target profile, and the top of that post corrects for the drop at that distance. Ingenious design and function.
    Who is selecting the items for your reviews??? You are IGNORING some of the most innovative and functional stuff on the market! WAKE UP!!!!

    September 25, 2019 12:20 pm
    • Commenter Avatar
      Ryan

      Diamond back is hot garbage

      June 4, 2021 6:56 pm
  • Commenter Avatar
    Bryan

    Midwest Industries Combat Rifle Sights are probably some of the best back up sights I've used. Low profile, minimalist, and rock solid.

    August 9, 2019 6:52 pm
  • Commenter Avatar
    TINY HELMS

    Hi folks! I enjoy all of the reviews on this website. Some of the best and balanced reviews that I have seen especially on firearms, etc.

    On the subject of back up iron sights:

    Tacticon Armament Flip Up Iron Sights

    I have two of these. I would be interested to hear if you have reviewed this brand.

    May 4, 2019 6:07 pm
    • Commenter Avatar
      David, PPT Editor

      Sorry, I don't think we have.

      May 4, 2019 6:26 pm
  • Commenter Avatar
    napior1985

    Hi, Thanks for valuable staff.

    Have you tried ERATAC ?

    March 8, 2019 11:59 am
  • Commenter Avatar
    numb1jeepguy

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

    January 1, 2019 6:15 am
  • Commenter Avatar
    Angel

    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.

    October 4, 2018 10:49 am
  • Commenter Avatar
    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.

    September 19, 2018 12:14 pm
  • Commenter Avatar
    Robert

    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.

    August 28, 2018 11:31 am
  • Commenter Avatar
    George Crum

    I learned on iron sights from my dad and for most situations and environments prefer them.

    July 25, 2018 8:25 am
  • Commenter Avatar
    Wzrd

    MBUS Pro. Spike's. I also have offset sights like the AAO pictured above on two of my magnified rifles. They're a very nice set for around $55 called XTS from Sportsman's Guide. Just like Deuck but 1/4 the price. I tried some that looked same from Amazon for $20 but they were crap. I'm guessing that's where AAO is sold?

    August 24, 2017 8:31 pm
    • Commenter Avatar
      Tom Smith

      I like an MBUS Pro front and KAC 600m rear. Neither were mentioned here. The KAC rear has elevation adjustment as well as wind age and it's easily adjusted. Sight in at 50 and your on out to 600.

      July 3, 2018 7:45 pm
      • Commenter Avatar
        Aiden H.

        How's the KAC Micro for distances less than 200m?

        December 27, 2018 6:47 pm
  • Commenter Avatar
    Mark

    On my M&P 15 Sport 2, my improved irons Blitzkrieg Components LLC Luminescent green chevron front sight post. I only needed Walmart-sold Blue Loc-tite to keep them in place, also. That is the extent of my back up irons, too. The sights line up now very rapidly, also..

    August 24, 2017 4:56 pm
  • Commenter Avatar
    Andrew Baca

    Have you had a chance to check a set of scalar works BUIS?

    August 24, 2017 4:40 pm
    • Commenter Avatar
      Michael

      ^Andrew Baca +1 OPS are the boss of iron sights

      August 24, 2017 8:50 pm
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