🟥 Glock 21 MOS Direct Mount Red Dots – Fast, Reliable, No Adapter Needed

Looking to add a red dot to your Glock 21 MOS without the extra bulk of a mounting plate? You’re in the right place.

At Mounts Plus, we carry a refined selection of direct-mount red dot sights designed specifically for the Glock 21 MOS platform. These optics fit directly onto your factory slide — no adapter required — giving you a lower profile, cleaner installation, and better performance under recoil.

Whether you're building a duty gun, a backcountry companion, or just want faster follow-up shots at the range, a properly fitted red dot will give your G21 the tactical edge.

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✅ Why Choose a Direct Mount Red Dot for Glock 21 MOS?

Glock’s MOS (Modular Optic System) allows you to mount optics directly to the slide. But not all red dots are created equal — some require bulky adapter plates, which raise the optic height, interfere with co-witnessing, and add unnecessary weight.

Direct mount optics solve that.

With the right red dot, you’ll benefit from:

• Lower profile – Better co-witness and faster sight picture

• Fewer moving parts – Less hardware means fewer failure points

• Cleaner fitment – Optic sits closer to the bore axis

• Better concealability – No plate sticking out under your optic

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🔍 Top Glock 21 MOS Direct Mount Red Dots

🔸 Holosun SCS MOS

• Solar-powered with auto-adjust brightness

• Directly mounts to Glock 21 MOS slide

• Green or red multi-reticle system

• Built for durability — handles .45 ACP recoil with ease

• No external battery changes — charges via sunlight or indoor lighting

🔸 C&H Precision Direct Mount Optic

• Enclosed emitter design for dirty or rainy environments

• Co-witness rear notch integrated into the optic body

• Includes mounting hardware for direct installation

• Available in red or green dot versions

• CNC machined from 7075 aluminum for hard use

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🔧 Glock 21 Compatibility – Gen 4 & Gen 5

Our direct mount red dots are tested and proven to fit:

• Glock 21 Gen 4 MOS

• Glock 21 Gen 5 MOS

• Factory slide cuts with Glock’s OEM MOS mounting system

These sights do not require adapter plates and can be installed with the included screws using standard hand tools.

Pro tip: Use blue threadlocker (Loctite 243 or equivalent) and torque the screws to manufacturer specs to maintain zero under recoil.

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🛒 Choosing the Right Red Dot for Your Glock 21

Not sure which optic to choose? Here’s how they stack up:

Feature	Holosun SCS MOS	C&H Direct Mount Optic
Mount Type	Direct to MOS slide	Direct to MOS slide
Power Source	Solar w/ internal batt	Standard CR battery
Emitter Type	Open reflex	Enclosed emitter
Ideal For	General use / carry	Harsh environments / duty
Co-Witness Support	Yes (lower 1/3)	Yes (rear notch built-in)

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📦 What’s Included

• Red dot optic (Holosun or C&H Precision)

• Glock-specific mounting screws

• Torx/Allen tool (model dependent)

• Quick-start install guide

• Battery (if applicable)

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🧠 Pro Tip

If you want a clean, plate-less install, go with the Holosun SCS. If you need rugged, enclosed reliability for duty use or bad weather, the C&H DMO is hard to beat.

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❓ Frequently Asked Questions (FAQ)

1. Do these red dots fit Glock 21 MOS without an adapter plate?

Yes. All optics on this page are designed to mount directly to the Glock 21 MOS slide without using a separate adapter plate.

2. Will these work with both Gen 4 and Gen 5 Glock 21 MOS?

Absolutely. These sights are compatible with both Gen 4 and Gen 5 Glock 21 MOS slides.

3. Can I co-witness my irons with these optics?

Yes. Some optics (like the Holosun SCS) allow lower 1/3 co-witness. Others (like the C&H DMO) include a built-in rear sight notch.

4. Do I need any special tools to install them?

No special tools are needed. You can install these red dots using the included screws and tools — just add threadlocker and follow torque specs.

5. Which optic is better for harsh conditions?

If you’re going to be outdoors in the rain or snow, the C&H enclosed optic is more protected and ideal for rugged use.