5 Best Glock 21 Red Dot Sights

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The Glock 21 is a formidable firearm I’ve spent countless hours on the range. 

I’ve earned my stripes with years of experience, by actually pulling the trigger. And among the many accessories I’ve tried, the Trijicon RMR Type 2 stands out as my top choice for a red dot sight. 

Trust me, finding the right sight for your firearm is no small task, and it took thorough testing to settle on the Trijicon RMR Type 2. I’ve put it through the paces, and it’s proven itself again and again. 

My aim is to share my hands-on experience, testing different sights and narrowing it down to the one that performed the best. I’ve analyzed them without bias and’ll give you the insights you need to make an informed decision. 

Top 5 Best Glock 21 Red Dot Sights

1. Trijicon RMR Type 2 – Best Choice

Trijicon RM06-C-700672 RMR Type 2 Adjustable LED Sight, 3.25 MOA Red Dot Reticle, Black
  • 3.25 MOA ADJUSTABLE LED RMR: Features an automatic...
  • UNIQUE PATENTED HOUSING SHAPE: Military-grade aluminum...
  • BATTERY CONSERVATION MODE: Automatically adjusts aiming...
  • BUTTON LOCKOUT: Sets RMR into automatic mode to prevent...

The Trijicon RMR Type 2 is a cutting-edge red dot sight that boasts durability, functionality, and aesthetics, offering shooters an unparalleled experience.

Adjustable LED Version: You know those moments when the lighting just isn’t right? This feature is a game-changer. With large, tactile buttons on each side, I found adjusting brightness to be a breeze. 

Whether in dim corridors or under the glaring sun, it’s always in the perfect setting.

Unique Design: Those distinct “horns” or “owl ears” aren’t just for show. 

This design proved its worth during my field tests by adding immense durability. It’s a visual signature that speaks of resilience and robustness.

Brightness Settings: With 8 different brightness levels, this sight never lets you down. 

Three settings are specially designed for low-light scenarios; the rest can light up the target even on a sun-soaked range. Trust me; it’s got you covered!

Automatic Mode: A feature I particularly enjoyed was the automatic brightness mode. It adapts to the environment without me having to fiddle with the buttons. 

But if I ever wanted to, turning it off was a snap. It’s smart without being complicated.

Battery Life: Powered by a CR2032 battery, it boasts a life ranging from 17,000 to 35,000 hours. 

Even in dark storage, it lasts around four years! That’s a friend that sticks around.

Why I Love It: What’s not to love? The RMR Type 2 offers so much in a sleek and rugged package. Its distinct design, brightness versatility, and long-lasting battery make it a cherished addition to my Glock 21.

My Experience 

Let’s get personal for a moment. I felt an instant connection when I mounted the RMR Type 2 on my Glock 21. 

Every feature whispered reliability, from its clear reticle to its rugged design. Shots were precise, and the sight handled the recoil like a champ. 

That iconic shape isn’t just for looks; it guarantees that the glass stays unbroken even with heavy use.


  • Robust, ready-for-anything build
  • Easy brightness adjustments for all conditions
  • Automatic mode that’s smart and helpful
  • Reliable, long-lasting battery
  • A design that’s both functional and eye-catching


  • The price might be a stretch for some, but it’s worth every penny

2. Trijicon SRO – Best for Competitive Shooting

Trijicon SRO Sight Adjustable LED 2.5 MOA Red Dot, Black
  • LARGE, UNOBSTRUCTIVE FIELD OF VIEW: Parallax-free and...
  • CLEAR, CRISP DOT: Fine-tuned, illuminated reticle,...
  • RED DOT PISTOL READY: Designed to fit on many of the...
  • SAME FOOTPRINT AS RMR: Mounts easily using the same...

The Trijicon SRO is a cutting-edge red dot sight designed with competition shooting in mind, featuring a larger window for better target acquisition.

Battery Life and Function: With a claim of 3-year battery life, the SRO can be a bit unpredictable depending on the battery brand used. 

Its top-inserted battery, sealed with a rubber O-ring, is a major improvement, though the cap can be difficult to handle.

Design and Durability: The circular housing is robust for range time and gun games, but it’s not the most rugged option out there. 

It’s been a trusted accessory for me, though its durability may not match some other industry leaders.

Controls and Adjustments: Adjusting the brightness is simple with the large + and – buttons. With eight brightness settings and specific button presses to suit preferences, it offers a nice amount of control and customizability.

Reticle and Glass Quality: The glass quality is decent, with minor distortion. 

The bright reticle with three size options ensures you can pick the best one for your eyes. 

Despite my astigmatism, it’s bright enough even in the desert sun.

Why I love it: The Trijicon SRO Red Dot provides a unique balance between functionality and innovation. 

The large window and advanced features like the top battery insertion make it stand out. It combines practicality and style and appeals to many shooting enthusiasts.

My Experience

I’ve had the pleasure of using the SRO in various shooting conditions. From desert sun to low-light IDPA matches, it has been a consistent performer. Its false dot in low angle sun and reflective nature in high brightness were interesting experiences.

Compare Trijicon SRO vs RMR


  • Large window for better target viewing
  • Top-inserted battery design
  • Good brightness adjustments
  • Sufficient for regular practice and matches


  • Unexpected brightness reflection in certain situations

3. Leupold DeltaPoint Pro – Strong Build

Leupold DeltaPoint Pro Red Dot Sight, 2.5 MOA Dot - Matte finish
  • Model #119688 - DeltaPoint Pro Red Dot Sight, 2.5 MOA...
  • Leupold’s Professional-Grade Red Dot Optical System...
  • This scopes comes with an illuminated reticle, which...
  • Motion Sensor Technology (MST) extends battery life by...
  • Design, Machined and Assembled in the USA. 100%...

The Leupold DeltaPoint Pro, a rugged and advanced red dot sight, is your go-to companion for accurate shooting and rapid target locking.

Unobstructed Field of View: With dimensions of 25.7 mm x 17.5 mm, it offers an unobstructed field of view, letting you see more than just the target. 

You’ll appreciate the broad perspective, whether you’re shooting at the range or in the wild.

Resistant to Water and Shock: Ever worried about dropping your sight or exposing it to extreme weather? With the Leupold DeltaPoint Pro, those concerns vanish. It’s been tested from -40°F to 160°F and is both water- and shock-resistant. That’s reliability you can count on!

Clear and Crisp Reticle: A clear and crisp reticle is what sets this sight apart. Whether you choose the 2.5 MOA, 6 MOA, or 7.5 MOA option, you get a reticle that ensures precision, helping you hit your mark every single time.

Why I love it: The Leupold DeltaPoint Pro isn’t just a sight; it feels like a part of me when I’m shooting. From its robust build to the clever MST feature, everything about it is designed with the shooter’s needs in mind.

My Experience 

Let me share with you my experience with this leupold sight on my Glock 21. The sight’s crispness and the wide field of view brought a new level of confidence to my shooting.

Its solid construction reassured me that it could handle the real-world pressures of shooting. 

Whether it was rapid target acquisition or adjusting the settings, everything felt intuitive and right at my fingertips.

Compare Leupold Deltapoint Pro & Trijicon SRO


  • An extensive field of view provides better situational awareness
  • A robust build ensures long-lasting durability
  • Resistant to extreme weather conditions
  • Multiple reticle options for a personalized experience
  • Intelligent features like MST conserve battery


  • Heavier compared to other similar sights

4. HOLOSUN HS507C X2 – Budget Alternative of Trijicon

HOLOSUN HS507C-X2 Classic Multi Reticle Red Dot Sight, Black
  • INCLUDES: Holosun HS507C-X2 Red Dot Sight | Coin...
  • LONG BATTERY LIFE: Features include Holosun’s Super...
  • ADVANCED TECHNOLOGY: There are 12 different brightness...
  • SHAKE AWAKE: Holosun’s Shake Awake Technology shuts...
  • Holosun optics with Solar Failsafe feature automatic...

It is a robust, multifaceted sight that impresses with its advanced features, packed into a sleek and lightweight design.

Multi-coated glass lens: The multi-layered glass coating on the Holosun 507c is more than just a feature; it’s an assurance of quality. 

Maximizing light wave transmission, it ensures a crisp and clear sight picture. Moreover, it’s designed to resist wear and shock. So, you can trust this lens to withstand the rough and tumble of the field.

Waterproof feature: Now, let’s talk about something we all worry about water damage. The IPX-6 rating means that this sight can endure underwater submersion for up to 30 minutes at a depth of 1 meter. 

That’s impressive and gives you the confidence to take on rainy weather or damp environments without a second thought.

Battery Life: When it comes to battery life and accompanying features, the Holosun 507c really stands out. Imagine a battery life ranging from 50,000 to 100,000 hours. That’s right; it won’t leave your side anytime soon. 

Brightness: Whether it’s a sunlit field or a dark forest at night, the Holosun 507c’s 10 daylight brightness settings and 2-night vision compatibility will not let you down. 

It’s like having a perfect vision in any lighting condition, a true companion for those who shoot in diverse environments.

Reticle: This sight offers a multi-reticle system with a 2 MOA dot and a 32 MOA circle, allowing flexibility and precision in targeting. 

Whether it’s pinpoint accuracy or tracking moving targets, this sight has got you covered. It’s like having different sights for different situations in one package.

Why I love it: There’s a lot to love about this sight. The combination of robust build, innovative features, and user-friendly design makes it a favorite. It’s not just a piece of equipment; it’s a reliable partner in the field.

My Experience

Pairing it with my Glock 21, the Holosun 507c truly shined. From its simple mounting due to the popular RMR footprint to its ease of use, it made every shot count. 

The lightweight design ensured that it never felt bulky or out of place. Whether I was hunting or just practicing, it consistently delivered top-notch performance.


  • Solar failsafe and shake-awake features
  • Exceptional battery life
  • Brightness settings for every scenario
  • Multi-reticle system for versatile aiming
  • Compact and lightweight


  • Presence of a slight bluish tint

5. Burris FastFire 3 – Best Value for Money

Burris FastFire Reflex Red Dot Sight for Rifles, Pistols and Shotguns, FastFire III (8 MOA Dot), Black (300236)
  • Convenient power button with three levels of brightness...
  • Tool-less wind age and elevation adjustments
  • Low Battery warning indicator
  • 8 MOA Dot Reticle
  • Tool-less wind age and elevation adjustments

Meet the Burris FastFire 3, a rugged and user-friendly red dot sight that’s a favorite among professionals and hobbyists alike.

Durability and Reliability: One thing you can’t ignore about the FastFire 3 is its solid build. This sight can take a beating thanks to its aluminum housing and still function flawlessly. It’s water-resistant and stays zeroed in no matter what.

Reticle Options: Options, folks! With the FastFire 3, you get different reticle choices, with the 3 MOA dot being a standout. This red dot stays true, clear, and bright whether you’re aiming up close or at a distance.

Glass and Lens Clarity: I can’t get over how crisp the lenses are. The glass on the FastFire 3 provides an exceptionally clear sight picture, even in low light conditions. It’s all about precision and comfort, with no distortion whatsoever.

Size and Weight: Size does matter, and the FastFire 3 nails it! It’s compact and lightweight, fitting on various firearms without adding unnecessary bulk. 

You’ll barely notice the additional 0.9 ounces, but you’ll surely appreciate the ease of use.

Windage and Elevation: Adjusting windage and elevation? Easy peasy! With two screws on sight, you can zero in your Glock 21 without a hassle. Each turn shifts the impact by 1 MOA, giving you the fine control you need.

Why I love it: From its versatile mounting options to the battery-saving standby mode, it’s a user-friendly sight that performs when you need it.

My Experience

Once out on the range, it felt as if the sight had been designed just for the Glock 21. The reticle was crisp, the adjustments responsive, and the overall experience was something I’ll never forget.

See Detailed comparison of Burris Fastfire 3 and Trijicon RMR.


  • High-quality build and durable design
  • Wide reticle options catering to different needs
  • Exceptional lens clarity
  • Compact and lightweight
  • Affordable price range


  • Could be improved in terms of resilience

Final Verdict

As a professional shooter with vast experience in testing these red dot sights on my firearm, I’ve concluded that the choice between these remarkable sights truly depends on individual needs and preferences. 

My thorough examination and hands-on experience lead me to choose Trijicon RMR type 2 as the winner, emerging as my top choice. It is an overall blend of what any serious shooter would desire, and while each sight has its strong points, this particular one encompasses those key elements that meet my specific demands.

Also Read my guide on common Glock 21 Problems.


What red dot fits Glock 21?

Several different red dot sights are designed for the Glock 21, including popular options like the Vortex Venom and the Burris FastFire III.

Can you put optics on a Glock 21?

Yes, the Glock 21 has the option to install an optic.

What is the best sight in distance for a pistol red dot?

Your zero for a red dot pistol sight should be set at a distance you would typically shoot from; if it’s a self-defense pistol, you would likely want to put your zero at around 10 yards.

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I'm Micheal, an avid shooter and hunting enthusiast from Texas. I'm a recreational shooter who loves to spend time at the range and enjoy learning about new firearms and gears. I love to write about guns and share my passion for shooting with others.

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