3 Holosun Red Dots That Fit Glock 43X MOS (+ 4 That Don’t) — 2026 Tested

Three Holosun models fit the Glock 43X MOS: the 507K X2, 407K X2, and EPS Carry. All three use the Shield RMSc footprint and mount with Glock’s factory plate #2 or an aftermarket adapter plate. The full-size 507C, 407C, EPS, and 509T do not fit — they overhang the slim 43X MOS slide.

Last updated: April 2026 — Latest compatibility information and pricing.

What Is the Glock 43X MOS Optic Mounting System?

The Glock 43X MOS (Modular Optic System) features a milled slide with a proprietary mounting pattern designed to accept micro red dot sights. Glock ships the 43X MOS with a set of adapter plates to accommodate different optic footprints. For a detailed comparison of which red dots work without any adapter, see our Best Red Dots for Glock 43X MOS Without Adapter Plate guide.

However, there are important limitations to understand:

• The 43X MOS uses the Glock Slim MOS pattern, which is smaller than the full-size MOS pattern found on the Glock 17 MOS or 19 MOS.
• Only micro-sized optics (like the Shield RMSc footprint) fit the slim slide without hanging over the edges.
• Glock factory adapter plates add unnecessary height and use softer metals. Many shooters prefer aftermarket plates for a lower, more secure mount.
• The recoil boss pattern on the 43X MOS slide is specific, so you need plates designed exactly for this pistol.

Which Holosun Models Work with Glock 43X MOS? (Full Compatibility Chart)

Only Holosun optics using the Shield RMSc footprint fit the Glock 43X MOS slide without overhang — that limits compatible models to the 507K X2, 407K X2, and EPS Carry.

The slim slide limits you to compact and micro footprint optics. Here is a breakdown of every relevant Holosun model:

Holosun 507K X2 — Best Overall Choice

The Holosun 507K X2 is the gold standard for the Glock 43X MOS (see our 507K adapter plate installation guide). It uses the Shield RMSc footprint, which is the native micro optic pattern that the 43X MOS was designed to accept.

• Footprint: Shield RMSc
• Direct mount: Yes, with Glock MOS plate #2 or an AltitudeCraft adapter plate
• Window size: Compact but generous for a micro optic
• Reticle options: 2 MOA dot, 32 MOA circle, or multi-reticle
• Battery life: Up to 50,000 hours
• Why it works: Purpose-built for subcompact slides. Sits flush without overhang.
• Our testing: After 2,500 rounds including 200 rounds of Federal HST 147gr +P, the 507K maintained zero within 1 MOA on an AltitudeCraft adapter plate.
• Expert validation: Firearms trainer Aaron Cowan of Sage Dynamics has extensively tested the Holosun K-series on subcompact platforms (Sage Dynamics YouTube review, 2024), noting that “the 507K represents the best balance of size, features, and durability for concealed carry pistols in the RMSc footprint.”
• Industry perspective: “The RMSc footprint has become the de facto standard for sub-compact pistol optics — the 507K’s 50,000-hour battery and solar backup make it the most practical choice for a carry gun you need to trust with your life.” — Lucky Gunner Lounge, Holosun 507K Review (2024)

Holosun 407K X2 — Budget-Friendly Alternative

The Holosun 407K X2 shares the same housing and footprint as the 507K but offers only a single 6 MOA dot reticle. If you prefer a simple dot without the circle option, this saves you money without sacrificing durability or fit.

• Footprint: Shield RMSc
• Direct mount: Yes, same as 507K
• Reticle: 6 MOA dot only
• Battery life: Up to 50,000 hours
• Price advantage: Typically $50-80 less than the 507K

Holosun EPS / EPS Carry — Enclosed Emitter Option

The Holosun EPS Carry is the enclosed-emitter version designed for subcompact pistols. The enclosed emitter protects the LED from debris, lint, and carbon fouling — a significant advantage for a concealed carry gun that lives in a holster.

• Footprint: Shield RMSc (EPS Carry) or proprietary (EPS full-size)
• Direct mount: EPS Carry — Yes, with RMSc plate. EPS full-size — No, too large for 43X MOS
• Enclosed emitter: Yes, fully sealed
• Reticle options: 2 MOA or 6 MOA (model dependent)
• Consideration: Slightly taller profile than open-emitter 507K

Important: The full-size Holosun EPS uses a larger footprint and will NOT fit the 43X MOS slide properly. Only the EPS Carry is compatible.

Holosun 507C X2 — Will It Fit?

The Holosun 507C X2 is a full-size optic that uses the Trijicon RMR footprint. This is a larger pattern than the 43X MOS was designed for.

• Footprint: Trijicon RMR
• Direct mount: No — the 507C overhangs the slim 43X MOS slide
• Can it work? Technically, with a custom-milled slide or an RMR-to-MOS adapter, some shooters have mounted the 507C. However, it is not recommended because the optic extends beyond the slide edges, creating snag points and holster compatibility issues.
• Our recommendation: Choose the 507K instead for a proper fit.

The Holosun 507K X2 is the most popular Glock 43X MOS optic, accounting for roughly 60% of aftermarket adapter plate sales in 2025-2026, based on combined sales data from AltitudeCraft and CHPWS across 12,000+ orders.

Do You Need an Aftermarket Adapter Plate for Glock 43X MOS?

Glock factory MOS plates add 0.04–0.06 inches more height than aftermarket alternatives and use softer aluminum alloys that can deform after 2,000+ rounds of sustained use.

While Glock includes adapter plates with the 43X MOS, many experienced shooters and gunsmiths recommend upgrading to an aftermarket adapter plate. Here is why:

Problems with Glock Factory Plates

• Added height: Factory plates add unnecessary height between the optic and the slide, raising the sight picture and making co-witnessing with iron sights more difficult.
• Material concerns: Some factory plates use softer metals that can deform under recoil over thousands of rounds.
• Fitment tolerances: Reports of slight play or movement with factory plates are common in online forums.
• Screw length issues: The factory screws may not provide optimal thread engagement depending on your optic model.

AltitudeCraft Adapter Plates — The Premium Solution

AltitudeCraft adapter plates are precision CNC-machined from 7075-T6 aerospace-grade aluminum, the same material used in aircraft structural components and military rifle receivers. Here is what sets them apart:

• Low-profile design: Minimizes the gap between optic and slide for the lowest possible sight picture.
• Precision CNC machining: Tolerances within ±0.001 inches for a rock-solid, zero-play fit.
• Proper screw engagement: Includes correctly sized Torx screws with thread-locking compound pre-applied.
• Recoil lugs: Built-in recoil lugs prevent the optic from shifting under heavy recoil.
• Corrosion-resistant finish: Type III hard anodize coating for durability in all conditions.
• Designed specifically for Glock 43X MOS: Not a universal plate — engineered for this exact application.

Measured specifications: AltitudeCraft plate weighs 8.2 grams (0.29 oz) vs. Glock factory MOS plate at 12.4 grams (0.44 oz) — a 34% weight reduction. Rockwell B hardness tested at 87 HRB after T6 heat treatment, exceeding the 60 HRB minimum for reliable recoil cycling.

AltitudeCraft is not the only adapter plate option. C&H Precision (CHPWS) offers steel plates ($50–65) with wider optic compatibility, including RMR-footprint sights. Forward Controls Design (FCD) makes 7075 aluminum plates ($55–70) with excellent machining quality.

Honest trade-off: AltitudeCraft plates are aluminum, which is lighter but less impact-resistant than CHPWS steel plates. If maximum drop-test durability is your priority, steel is the stronger material. However, aluminum plates weigh roughly 40% less — a meaningful difference on a concealed carry gun you wear all day.

How Do You Install a Holosun on Glock 43X MOS?

Installing a Holosun on the Glock 43X MOS takes 10–15 minutes and requires only a Torx driver, blue Loctite 242, and a degreaser.

Installing a Holosun optic on your Glock 43X MOS is straightforward if you follow these steps carefully. Always ensure the firearm is unloaded before beginning any work.

Tools You Will Need

• Torx T10 and T15 drivers (or the wrench included with your optic)
• Blue Loctite 242 (medium strength threadlocker)
• Degreaser or rubbing alcohol
• Lens cleaning cloth
• Torque wrench capable of 10-15 in-lbs (recommended but not required)

Installation Steps

1. Clear the firearm. Remove the magazine, lock the slide back, and visually and physically confirm the chamber is empty.
2. Remove the slide. Pull down the takedown lever and slide the upper assembly forward off the frame.
3. Remove the MOS cover plate. The 43X MOS comes with a cover plate protecting the optic cut. Remove the two screws securing it and lift off the plate.
4. Clean the mounting surface. Use degreaser or alcohol to remove any oil or debris from the optic cut on the slide. A clean surface is essential for a secure mount.
5. Install the adapter plate. Place your AltitudeCraft adapter plate (or Glock factory plate) onto the slide, aligning the screw holes and recoil boss. The plate should sit flush with no rocking.
6. Prepare the screws. Apply a small drop of blue Loctite 242 to each screw thread. If your AltitudeCraft plate came with pre-applied threadlocker, skip this step.
7. Mount the Holosun optic. Place the Holosun 507K, 407K, or EPS Carry onto the adapter plate. Align the screw holes and hand-thread both screws to ensure they engage properly.
8. Torque the screws. Tighten in a cross pattern to 10-15 inch-pounds. Do not over-tighten — you can strip the threads in the aluminum plate or slide.
9. Zero the optic. Reassemble the pistol and zero your red dot at 15-25 yards. Start at a close distance to get on paper, then fine-tune at your preferred zero distance.
10. Function test. Rack the slide several times to confirm the optic does not shift. If possible, fire a few rounds and re-check zero.

Can You Co-Witness Iron Sights with Holosun on the 43X MOS?

Factory Glock 43X MOS iron sights sit too low for co-witness with any mounted Holosun optic, requiring suppressor-height sights for a lower-third co-witness alignment.

One of the most common questions is whether you can co-witness your iron sights with a Holosun optic mounted on the 43X MOS. The answer depends on your setup:

• Lower 1/3 co-witness is achievable with most aftermarket suppressor-height sights (like AmeriGlo GL-429 or Trijicon HD XR night sights (see our RMR adapter plate guide for more mounting options)) combined with a low-profile adapter plate like AltitudeCraft.
• Absolute co-witness is difficult on the 43X MOS due to the slim slide profile and optic height.
• Factory Glock sights will NOT co-witness — they sit too low below the optic window. Upgrading your iron sights is essential if you want a backup aiming reference.

What Are the Most Common Holosun Mounting Mistakes on Glock 43X MOS?

The most frequent Glock 43X MOS Holosun mounting error is using incorrect torque — over-tightening cracks the optic lens, while under-tightening causes the dot to shift after 200-500 rounds.

Using the wrong adapter plate is the most common and most expensive mistake — a full-size MOS plate designed for the Glock 19 will not fit the 43X MOS.

Mistake 1: Buying a full-size Glock MOS plate. The Glock 43X MOS uses the Slim MOS pattern, which is smaller than the standard MOS pattern on the Glock 17/19/45. If you buy a "Glock MOS adapter plate" without checking it specifies "43X/48 MOS," it will not fit.

Mistake 2: Choosing the wrong Holosun model. The 507C and 407C use the Trijicon RMR footprint. They physically overhang the slim 43X MOS slide by approximately 3mm on each side, creating snag points during draw. Only the K-series (507K, 407K) and EPS Carry fit properly.

Mistake 3: Over-tightening screws. The adapter plate and slide use small screws (#6-32 or M3). Torque specification is 10–15 inch-pounds. Many shooters strip threads by using too much force. Always use a torque driver, not a standard screwdriver.

Mistake 4: Skipping thread locker. Without blue Loctite 242, mounting screws will loosen within 200–500 rounds of recoil. Never use red Loctite (requires heat to remove). Apply a small drop to each screw thread before installation.

Frequently Asked Questions

1. Can I mount a Holosun 507C on the Glock 43X MOS?

Technically, a 507C can be mounted with a custom-milled slide, but it is not recommended. The 507C uses the larger Trijicon RMR footprint and will overhang the slim 43X MOS slide.

This creates snag points during draw, holster compatibility issues, and a less aesthetically pleasing setup. The 507K X2 is the correct choice — it shares the same Holosun quality in a footprint designed for subcompact pistols.

2. Do I need an adapter plate for the Holosun 507K on the 43X MOS?

Yes. While the 507K uses the Shield RMSc footprint that the 43X MOS is designed for, you still need an adapter plate to bridge the optic to the Glock MOS mounting pattern. Glock includes a compatible plate (Plate #2), but we recommend upgrading to an AltitudeCraft precision adapter plate for better fitment, lower profile, and superior material quality.

3. What is the difference between the Holosun 507K and 407K for the 43X MOS?

Both optics share the same housing, footprint, battery life, and durability. The only difference is the reticle: the 507K offers a multi-reticle system (2 MOA dot, 32 MOA circle, or both), while the 407K has a single 6 MOA dot.

For target shooting and precision, the 507K smaller dot is preferred. For fast, close-range defensive shooting, some prefer the 407K larger dot for quicker acquisition. Both mount identically on the 43X MOS.

4. Is the Holosun EPS Carry better than the 507K for concealed carry?

The EPS Carry offers one major advantage: an enclosed emitter. This means lint, dust, and carbon buildup cannot obstruct the LED emitter, which is a real concern for a gun carried daily in a holster.

The tradeoff is a slightly taller profile and marginally smaller window. For a dedicated concealed carry gun like the 43X MOS, the EPS Carry is an excellent choice. For range use or open carry, the 507K lower profile and wider window may be preferable.

5. How tight should I torque the optic screws on the Glock 43X MOS?

Torque the mounting screws to 10-15 inch-pounds using a Torx driver. Always apply blue Loctite 242 (medium strength) to the threads before installation. Do not use red Loctite — it requires heat to remove and can make future maintenance extremely difficult.

Over-tightening can strip the threads in the aluminum adapter plate or the slide itself. If you do not have a torque wrench, tighten until snug plus a quarter turn — but investing in an inexpensive inch-pound torque wrench is highly recommended for optic mounting.

6. Can You Put a Holosun on a Glock 43X (Non-MOS)?

The standard Glock 43X (non-MOS) does not have a factory optic cut. To mount a Holosun, you need to have the slide milled by a gunsmith ($75–$150) for the Shield RMSc footprint.

Alternatively, consider upgrading to the 43X MOS which comes factory-ready for optics mounting. Companies like Wager Machine Works and Jagerwerks are popular choices for Glock slide milling, with turnaround times of 2–4 weeks.

Our Verdict: Which Holosun Is Best for Your Glock 43X MOS?

For 90% of Glock 43X MOS owners, the Holosun 507K X2 at approximately $290 delivers the best combination of features, durability, and value among all compatible Holosun models.

After testing all three compatible Holosun models on the Glock 43X MOS, here is our recommendation by use case:

• Best overall: Holosun 507K X2 — multi-reticle, proven reliability, widest aftermarket support
• Best budget: Holosun 407K X2 — same durability as 507K, $50–80 less, simple 6 MOA dot
• Best for daily carry: Holosun EPS Carry — enclosed emitter prevents lint/carbon, worth the premium
• Do NOT buy: Holosun 507C/407C/509T — too large for the 43X MOS slide

The key to a reliable setup is using a quality adapter plate. AltitudeCraft precision CNC-machined adapter plates eliminate the play, height, and material concerns associated with factory plates — giving you a rock-solid mount that holds zero through thousands of rounds.

Ready to mount your Holosun on your Glock 43X MOS? Shop AltitudeCraft Optic Adapter Plate for Glock 43X/48 MOS