Best AR-15 Rear Sights for 2026: What Builders Actually Buy

Here are the AR-15 rear sights GunPartPicker builders picked most when they bought a rear sight on its own, from our build data for July through September 2026, with what each one costs today.

• Best overall: Magpul MBUS Gen 2 Rear, about $37 to $55, the most picked rear sight at 18.7% of rear sight picks.
• Best under a magnifier: Mission First Tactical Flip Up Polymer Rear, about $45, second at 11.7%.
• Best budget: NcStar VISM Pro Series Flip-Up Rear, about $26 to $39, third at 9.5% and the cheapest of the top five.
• Best steel: Magpul MBUS Pro Rear, about $90 to $120, fourth at 9.2% and the most picked steel rear.
• Best offset: Ultradyne C4 Offset Folding Rear, about $160 to $240, fifth at 8.9% and the most picked offset rear.

Most addedMagpul

Magpul AR-15 Flip-Up MBUS Gen 2 Tactical Rear Sight Black

In stock

$36.99 at KY Gun CompanyCompare 5 stores+ Add to build

Also popularMission First Tactical

Mission First Tactical AR-15 Rear Sight Flip Up Polymer Black

In stock

$44.99 at Classic FirearmsCompare 7 stores+ Add to build

Also popularNcStar

NCSTAR Vism PRO Series Flip-Up Rear Sight

In stock

$26.09 at KY Gun CompanyCompare 5 stores+ Add to build

Also popularMagpul

Magpul MBUS PRO Rear Sight - Black

In stock

$109.95 at CMMGCompare 6 stores+ Add to build

Ultradyne

Ultradyne USA C4 Offset Folding Rear Sight

In stock

$159.99 at Optics PlanetCompare 4 stores+ Add to build

The Picks, With a Verdict on Each

Best Overall: Magpul MBUS Gen 2 Rear

The MBUS Gen 2 is a polymer flip up rear with two apertures and windage adjustment. Hit the grooved tab on either side and it springs up and locks. Hit it again and it folds flat behind your optic.

It's the default backup rear for a rifle with a red dot or a flattop upper. Builders agreed: it took 18.7% of rear sight picks, well ahead of MFT's rear in second.

What we like

• Magpul's listing says it uses less than 1 inch of Picatinny rail and locks on with an included steel crossbolt.
• It sits at the same height over bore as standard A2 irons, so it pairs with any standard height front.
• It's about $37 to $55 at the stores we track.

Watch out for

• It's reinforced polymer. The MBUS Pro below is the steel version and costs about twice as much.
• It stands 1.6 inches tall deployed and 0.5 inches folded, per Magpul, a bit taller folded than the newer MBUS 3.
• Prices spread almost $20 between stores, so check the card for the low one.

Best Under a Magnifier: Mission First Tactical Flip Up Polymer Rear

MFT built this rear around a shroud that covers the aperture when it's folded. That keeps grit and knocks off the part you look through. The sight is slim enough to sit under current magnifiers and optics, according to MFT.

It's the rear to buy if you run a red dot with a flip to side magnifier behind it, where rail space and height are tight. It took 11.7% of rear sight picks, second overall.

What we like

• Its two peep apertures sit on the same plane, which MFT says gives a perfect co-witness.
• It folds to the rear, the correct direction if the rifle is dropped, according to the listing.
• It's about $45 at the stores we track.

Watch out for

• You need a flat head screwdriver to adjust windage, per MFT.
• It's polyamide, a reinforced polymer, not metal.
• At about $45, it costs about the same as the Magpul MBUS Gen 2, so it isn't a cheaper option.

Best Budget: NcStar VISM Pro Series Flip-Up Rear

NcStar's Pro Series rear is a spring loaded flip up sight with an A2 style dual aperture, one large and one small. A knurled knob adjusts windage, and the low profile body folds flat under most scopes, per the listing.

Pick it if you want a backup rear for the least money and you'll pair it with a standard height front. It took 9.5% of rear sight picks, third overall, and it's the cheapest sight in the top five.

What we like

• NcStar lists an aluminum body with a steel A2 rear aperture, not all polymer.
• It mounts to a MIL-STD-1913 Picatinny rail, and the listing says a mounting tool comes in the box.
• It's about $26 to $39 at the stores we track.

Watch out for

• NcStar lists the rear at 2.3 oz, heavier than the 1.3 oz Magpul MBUS Gen 2.
• The listing text describes the full front and rear set. This card is the rear only, so check the product page before you order.
• It's in stock at only three of the stores we track.

Best Steel: Magpul MBUS Pro Rear

The MBUS Pro rear is the all steel version of Magpul's backup sight. It has large and small same plane apertures, windage adjustment, and positive detents that hold it up or down. Stowed, it sits only 0.375 inches above the rail at its midpoint, per Magpul.

It suits a duty or hard use rifle where you want metal and a lower folded height than the polymer MBUS. It took 9.2% of rear sight picks, fourth overall and the most of any steel rear.

What we like

• Magpul lists all steel construction.
• At 0.375 inches stowed, it sits lower than the polymer MBUS Gen 2.
• It stands at standard AR sight height when deployed, so it works with any standard front.

Watch out for

• At about $90 to $120, it costs about twice the MBUS Gen 2.
• Prices spread more than $30 between stores, so check the card.
• For a matched set, pair it with the MBUS Pro front, which Magpul says needs a rail height mount, not a low profile gas block.

Best Offset: Ultradyne C4 Offset Folding Rear

The C4 rear pairs with Ultradyne's C4 front, whose post has a hole through the middle. Line them up and you get what Ultradyne calls a circle within a circle sight picture, so you can see the target while you align the sights. It mounts at an offset, beside your scope rather than behind it.

Pick it if you run an LPVO or a fixed power scope and want offset irons you can reach by rolling the rifle. It took 8.9% of rear sight picks, the most of any offset rear.

What we like

• The circle within a circle picture leaves the target visible through the front post, per Ultradyne.
• It mounts to any MIL-STD-1913 Picatinny rail, according to the listing.
• It folds, so it stays clear of your optic until you need it.

Watch out for

• At about $160 to $240, it's the most expensive rear on this page.
• The sight picture depends on the matching C4 front, so budget for both.
• Prices vary by more than $100 between stores, so check the card for the low one.

Most Picked Rear Sights

Magpul takes 27.9% of rear sight picks between the MBUS Gen 2 and the MBUS Pro. MFT is second at 11.7%, NcStar third at 9.5% and Ultradyne fifth at 8.9%.

Troy's tritium Di-Optic rear sits sixth at 4.7%. We don't card it here. If you want tritium on a rifle, our iron sights guide covers Troy's offset sets.

How Do You Pick a Rear Sight?

Start with the front. A rear only works with a front at the height it expects. The Magpul, MFT and NcStar picks work with standard height fronts on a rail at the same plane as your receiver. The Ultradyne rear wants its own C4 front.

Then decide on folding or offset. A folding rear sits behind your red dot and flips up if the dot dies. An offset rear sits at 45 degrees and suits a magnified scope.

Buying a rear on its own makes sense when your barrel already has an A2 front sight base, or when you want a different rear than a set would give you. If you need both, our iron sights guide covers matched sets.

How We Pick

Each pick is the rear sight that builders added to a GunPartPicker build most often for its job. Every spec comes from the product's own listing or the maker, and the prices on the cards are live.

Related Guides

• AR-15 front sight guide
• AR-15 iron sights guide
• AR-15 red dot and optic guide

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