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Reflex Sights vs. Red Dot Sights

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Since their introduction to the firearm market, reflex sights have become some of the most popular optic variants available. Their compact and lightweight designs make them a solid choice for lightweight rifle builds and other compact platforms.  

Today, there is a vast selection of reflex sights available, with red dot sights being the most popular subcategory. Despite this, there is still a lot of confusion and misinformation on what constitutes a ‘red dot sight’ versus other reflex sights. Many enthusiasts use the terms interchangeably, but there are a few important differences that distinguish a red dot from other reflex optics. The easiest way to put it is like this: “all red dot sights are reflex sights, but not all reflex sights are red dot sights.” 

In this article, we will discuss the differences that make red dot sights distinct from other forms of reflex sights, and why it matters when talking about today’s optics. 

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Is It Reflex or Red Dot Sight?  

The term ‘reflex sight’ encompasses multiple optic variants. In fact, popular optic types like red dots and holographic sights are both subcategories of reflex sights. In fact, there are many different types of reflex sights, which may differ greatly in construction or technology. Still, at their core, their function remains the same: superimposing an emitted reticle against a lens for faster aiming. 

Arguably, one of the greatest benefits reflex sights and red dots provide is their enhanced accuracy and target acquisition features. When using these optics, all you need to do is put your reticle on the target, so long as it’s properly zeroed

Moreover, your peripheral vision increases drastically with reflex/red dot sights. By design, reflex sights allow you to shoot with both eyes open. By doing this, you gain a better image of not only your target, but its surroundings. This grants you better situational awareness, giving you an edge in shooting scenarios that involve movement or engaging moving targets. 

Red Dot Sights vs. Open-Emitter Reflex Sights

What Are Their Differences 

Red Dot Sights 

As we mentioned before, red dot sights are a popular subcategory of reflex sights. Red dot sights are distinguished by their enclosed, dual-lens construction. In contrast to other reflex sights, which might have a single lens and an open emitter, red dot sights are a fully enclosed system, where the emitter is enshrouded in a single assembly with a forward and rear lens. This means that adjustments to your elevation or windage will affect the whole assembly rather than just the position of an emitter.  

Red dot sights can come in an array of different sizes. Full-size red dots are the more traditional option, but as technology has improved, many manufacturers have gravitated towards a ‘micro red dot’ design. These optics work the same way as their larger full-size counterparts, but they’re much smaller by comparison, making them lighter and more mobile for close-quarters agility.   

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Red Dot Sight Options 

Primary Arms Optics: Our red dots are among the most popular optics we sell. Our Classic Series® 25mm Push Button Red Dot Sight is a solid optic that’s great for all budgets and builds. It’s designed to stand up to tough use in harsh conditions and has a long battery life that lasts upwards of 25,000 hours of run time. Another option is our SLx® Advanced Rotary Knob Microdot. It’s just as durable but much smaller in size, making it perfect for compact platforms or if you just want a low-profile optic. 

Aimpoint: Aimpoint is one of the most well-renowned optic manufacturers. They specialize in making durable red dot sights, and some of their most popular options are the Micro T-2, COMPM5, and the ACRO P-2. The Micro T-2 is one of the most popular optics offered by Aimpoint. It has a small footprint and is built with incredibly durable components. It projects a 2 MOA dot reticle and has a battery life that can last upwards of 50,000 hours of constant runtime. Lastly, it has four-night vision compatible brightness settings, and 8 daylight ones.  

The COMPM5 is very similar to the Micro T-2, but it’s built with more robust materials and is larger in size. Its biggest differences are its battery type, overall size, and durability. Instead of taking CR2032 batteries, the COMPM5 uses AAA batteries. It’s also slightly larger in size and is more resistant to water exposure, being submersible to up to 45 meters. Besides these differences, it has the same reticle, battery life, and brightness settings.  

Finally, the ACRO P-2 is a pistol red dot sight. It’s designed for handguns and has a 3.5 MOA dot reticle, a 50,000-hour battery run time, 4-night vision settings, 6 daylight settings, and can be submerged in up to 35 meters of water. It utilizes a low-profile mounting system, making it a great option for cowitnessing with your pistol’s iron sights.  

Holosun AEMS Green

Holosun: One of the most popular red dot manufacturers is Holosun. They’re well-known amongst enthusiasts and they produce high-quality red dot sights for a variety of platforms. Their AEMS model is a low-profile, enclosed red dot sight capable of producing three different reticle patterns. It also has a long battery life that lasts up to 50,000+ hours and can come with a Solar Failsafe, depending on the model.  

Another solid option is the HS530G-RD. Constructed out of titanium, it’s one of the most durable optics offered by Holosun. Like the AEMS, it uses multiple reticles and has a similar battery life, albeit without the option of having a solar failsafe. 

Vortex Optics: Vortex produces many optics, but their most popular red dot sight is the SPARC. The SPARC is a microdot with a low profile and light weight. It features a durable aluminum construction and has a battery life of upwards of 50,000 hours. There are additional models too, such as the SPARC SOLAR, which has a solar unit. This model has an even longer battery that can last upwards of 150,000 hours, which is over 17 years.  

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Trijicon: The MRO from Trijicon is a great red dot option. The large objective lens provides a wide field of view, showing a proper image of the target and its surroundings. The MRO uses either a green or red 2 MOA dot depending on the model, but there are others to choose from. The MRO HD is a direct upgrade to the MRO that uses a circle dot reticle instead. The HD variant also has upgraded lenses and an increased battery life.  

Open-Emitter Reflex Sights 

As we said before, reflex sights encompass a wide variety of optics. So technically speaking, every optic in this list is a reflex sight. Still, not all reflex sights can be considered red dot sights. One such sight option is an open emitter reflex sight. As their name suggests, they use an open emitter design, meaning the emitter diode that projects the reticle isn’t enclosed within a tube or housing like on red dot sights.  

In order for an optic to be considered a red dot sight, it must feature a fully enclosed design. Instead of two lenses, open-emitter reflex sights only have one. The light from the emitter diode is collimated onto the lens, which reflects to your eye to create the reticle picture.  

One of the main concerns with this style of reflex sight is that their emitter diodes can be exposed to dirt and debris when in field conditions. Though they’re durable optics when built with quality materials, the emitter diode can become occluded if any kind of debris elements get onto the optic. Still, they are incredibly reliable and can often be much smaller than most conventional red dot sights.  

One of the most popular variants is the mini-reflex sight. Mini-reflex sights are exactly as their name describes, small open-emitter reflex sights. They’re much smaller than both full-size and micro red dots, making them useful on handguns or on rifles as a backup/offset sight. 

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Open-Emitter Reflex Sight Options 

Primary Arms Optics: Our Classic Series® 21mm Micro Reflex Sight is a mini reflex sight that uses a 3 MOA dot reticle. It uses the popular RMSc mounting footprint, making it compatible with many popular sub-compact pistols, and it’s an incredibly lightweight optic that has a battery life of up to 50,000 hours.For larger handguns, our Classic Series® 24mm Micro Reflex sight and new GLx® RS-15 are great options. Our Classic Series 24mm Micro Reflex Sight is optimized for full-size carry pistols. It’s lightweight and has a battery life of up to 40,000 hours.  

New to our lineup is the GLx RS-15 mini-reflex sight. It’s the first Primary Arms Optics production model to feature our ACSS® Vulcan® Dot reticle. It has a large lens, a top-loading battery compartment, and comes with our AutoLive® feature for maximum run time. 

Holosun 510C FDE

Holosun: Holosun makes a large share of reflex sights. One of their most popular full size reflex sights is the 510C. Designed for use on carbines, it’s an open emitter reflex sight with a wide field of view and long battery life of up to 50,000 hours. Like some other Holosun optics, the 510C has a built-in Solar Failsafe to maximize its battery life. 

Holosun also produces mini-reflex sights like the 507C and 507K, for example. The 507C is designed for use on full-size pistols, has multiple brightness settings including night vision options, and comes with their Solar Failsafe. Conversely, the 507K is designed for sub-compact pistols. The 507K has the same amount of brightness settings but doesn’t have a Solar Failsafe option due to its compact size.  

Select models of the 507C and 507K come with our ACSS Vulcan reticle. If you’re unfamiliar with the ACSS Vulcan reticle, our guide on Holosun Red Dots with the ACSS Vulcan reticle is worth checking out. It breaks down everything you’ll need to know about the reticle system as well as the specifics on the optics that utilize it. 

Vortex Optics: Some of the most popular optics from Vortex are their mini-reflex sights. They have a few models available, such as the Venom, Viper, and Defender. The Venom and Viper are designed for use on full-size pistols, and they have a variety of features. Both optics can either come with a 3MOA or 6MOA dot reticle and have batteries that can last up to 150 hours on the highest setting. While they’re similar, they have different battery sizes, slightly different dimensions, and lens shapes.  

The Defender differs in size from the Venom and Viper since it was designed for use on sub-compact pistols. It’s also available with either a 3MOA or 6MOA dot reticle, but it comes with an automatic shutoff feature to maximize its battery life.  

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Trijicon: Some of the most popular mini-reflex sights available are the RMR and SRO from Trijicon. Both optics use the popular RMR footprint, have multiple reticle options, and have battery lives of up to 50,000 hours. The main difference in the optics is their shape. The RMR uses a rectangular lens, while SRO uses a round lens. Both optics function the same, but the RMR has a lower profile than the SRO, while the SRO offers a better field of view. The RMR has an updated HD variant as well. The RMR HD is a direct upgrade to the RMR, featuring larger buttons, a larger lens, and a top loading battery compartment.  

Leupold: Like Vortex, Leupold is known primarily for their variable power optics. That said, they produce some popular mini-reflex sight options like the Delta Point Pro. The Leupold Delta Point Pro is an open emitter mini-reflex sight that can come with either a 2.5 MOA or 6 MOA dot reticle. It’s designed for use on full-size pistols and has a battery life that can last up to 300 hours when on the highest brightness setting. For maximum run time, it has motion sensors that automatically turn the dot on and off. Finally, it’s available in either a black or FDE finish.  

Holographic Sights 

Holographic sights, like the EOTech EXPS-3 and Vortex AMG UH-1 Gen II, are another type of reflex sight that uses a very different technology than red dots, but the result is largely the same. While red dot sights bounce light off a singular point to project the reticle on the objective lens, holographic sights use multiple surfaces to bounce the light. This creates their iconic hologram reticle, projecting between the optic’s lenses. If you’re interested in learning more, our guide on holographic vs red dot sights breaks down both optic variants in a head-to-head comparison. 

Holographic Sight Options 

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EOTech: Perhaps one of the most popular holographic sight manufacturers is EOTech. They are a highly regarded manufacturer of holographic sights, with their EXPS3-0 and 512-0 being some of their most sought-after models. The EXPS3-0 is currently one of EOTech’s most popular sight options. Its battery life can last upwards of 1,000 hours, it has night vision capabilities, and it’s constructed with high quality materials to make it capable of operating in tough conditions.  

Likewise, the 512-0 is another great optic from EOTech. It’s a lot like the EXPS3-0, but it has a larger mounting footprint. This is because the 512-0 takes AA batteries instead of CR123s, which gives it a much longer battery life that lasts upwards of 5,000 hours. Unlike the EXPS3-0, the 512-0 doesn’t have any night vision capabilities, but it still has the same circle dot reticle while having a longer lasting battery life.  

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Choosing the Best Sight for Your Needs 

With so many optics available, there’s a good chance that you don’t know where to start your search. The examples mentioned above are only a few drops in the sea of optic choices. So that begs the question, which one is best?  

None of them are. The best optic is the one that fits your needs best. For instance, if you’re building a duty-grade AR-15 to be used in service or intense shooting competitions, a full-size red dot sight or microdot is recommended. Conversely, if you’re wanting an offset red dot or a more versatile optic for your concealed carry pistol, a mini-reflex sight or pistol red dot is the better choice. 

If you’re shopping for a pistol red dot or mini-reflex sight, our article on what to consider with a pistol red dot has a lot of rich information on the topic. Be sure to check it out if you’re not sure where to begin your search. 


There are a lot of reflex sights available today, so it can be hard to remember all the subtle differences. Though each subcategory may be distinct in construction or design, they all provide similar advantages in making hits on target. Regardless of which sight you choose, each reflex sight aids in facilitating quick sight and target acquisition, taking your shooting experience and accuracy to the next level. 

With so many models available to you, it’s a good idea to keep researching into them by checking out what the manufacturers their websites and the model’s manual. The last thing you’d want is to end up with an optic that doesn’t fill the role you need it to.   

Keeping up to date on what’s available is key to making an informed decision. So, if you’re still feeling lost, our red dot buyer’s guide and our article on the five things to know when buying a red dot are full of great insights.