Choosing the right red dot sight can make a significant difference in how quickly and naturally an optic can be used with both eyes open.
With numerous models available, it can be difficult to understand the differences in reticle size, window design, battery life, durability, and mounting options.
This guide explores popular red dot sights from Aimpoint, Trijicon, Holosun, and Vortex.
It also explains how red dot sights work, the benefits of both-eyes-open viewing, the main types available, and the factors worth considering before choosing a model.
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| 1) Aimpoint Micro T-2 |  |
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| 2) Aimpoint PRO |  |
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| 3) Trijicon MRO |  |
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| 4) Trijicon RMR Type 2 |  |
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| 5) Holosun HS510C |  |
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| 6) Holosun EPS |  |
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| 7) Vortex StrikeFire II |  |
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What Is a Red Dot Sight?
A red dot optical sight is an optical sight with an illuminated reticle, typically a small red dot, for aiming. Unlike with conventional iron sights, it is not necessary to line up the front and rear sights.
Most red dot sights come with 1x power magnification and offer unlimited eye relief, which means that the dot can be seen from many eye positions.
This type of design can be used to achieve a natural, both eyes open viewing view of the surrounding scene. There are various types of red dot sights such as open-reflex, enclosed-emitter and tube-style, each with different reticle sizes, batteries, and durability.
How Do Red Dot Sights Work?
A red dot sight works by using an LED emitter to project an illuminated reticle onto a specially coated optical lens. The lens reflects the light from the LED back toward the user’s eye while allowing the target and surrounding scene to remain visible.
Because the projected dot appears to be on the same viewing plane as the target, the user can place the dot over the desired point without aligning traditional front and rear sights.
Most red dot sights offer 1× magnification and unlimited eye relief, allowing the sight picture to be viewed naturally with both eyes open. Brightness controls help keep the dot visible under different lighting conditions.
Benefits of Using a Red Dot Sight With Both Eyes Open
Using a red dot sight with both eyes open can provide a more natural and unrestricted viewing experience. Because most red dot sights offer unlimited eye relief, the user does not need to maintain a precise eye position behind the optic.
Keeping both eyes open can also provide a wider field of view and better awareness of the surrounding environment.
The illuminated dot provides a simple aiming reference without requiring alignment of separate front and rear sights.
Red dot designs with larger windows, such as the Holosun HS510C, can provide a particularly open sight picture, while compact models such as the Aimpoint Micro T-2 emphasize portability and durability.
Types of Red Dot Sights
Red dot sights come in several designs, each with different optical and physical characteristics.
Open-reflex sights have an exposed emitter and an open viewing window, providing a broad sight picture. Examples include the Trijicon RMR Type 2 and Holosun HS510C.
Enclosed-emitter sights place the LED inside a protective housing, helping shield it from dust, moisture, and debris; the Holosun EPS is an example.
Tube-style red dots, such as the Aimpoint Micro T-2, Aimpoint PRO, Trijicon MRO, and Vortex StrikeFire II, use a cylindrical housing around the optical system.
These designs differ in size, weight, window dimensions, battery systems, durability, and mounting requirements.
Red Dot Sight Both Eyes Open
1) Aimpoint Micro T-2
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The Aimpoint Micro T-2 is a compact 1× red-dot sight that offers a natural sight picture with both eyes open and rapid target acquisition.
It has a 2 MOA red dot for aiming precision as well as unlimited eye-to-optic distance for the dot to be viewed, meaning that eye relief does not need to be set.
Aimpoint also has a clear rear lens cover, so that the sight can be used even with the cover closed.The Micro T-2’s rugged aluminium housing ensures durability in challenging outdoor environments.
Damp-proof to 25 m (80 ft) of water and rated to function between −45°C and +71°C. Optic has several brightness levels – four are set for night vision, and eight are designed for daylight.
According to Aimpoint, the sight will give up to 50,000 hours of battery life at daylight setting 8.
Key Specifications
- Magnification: 1×
- Dot size: 2 MOA
- Eye relief: Unlimited
- Weight: Approximately 94 g (3.3 oz), without mount
- Battery: CR2032
- Battery life: Up to 50,000 hours
- Water resistance: 25 m (80 ft)
- Night vision: Compatible
- Operating temperature: −45°C to +71°C
Pros
- Compact and lightweight
- Excellent battery life
- Rugged construction
- Unlimited eye relief
- Multiple brightness settings
- Night-vision compatibility
Cons
- Smaller viewing aperture than some open-reflex designs
2) Aimpoint PRO
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The Aimpoint PRO (Patrol Rifle Optic) is a small, red-dot sight that focuses on fast target acquisition and a natural two-eyes-open sight picture.
Sight picture is simple to use, with a 2 MOA red dot, no parallax, and unlimited eye relief. In addition to the transparent rear lens cover, Aimpoint also offers a cover that will permit the optic to be used with the covers closed.
High-quality aluminum body with semi-matte anodized finish from the PRO. It is suitable for harsh environments and waterproof to 45 meters (150 feet).
Optic offers 4 night vision and 6 day settings. The battery life is up to 30,000 hours at daylight setting 7, which is the longest possible setting, or over 3 years of continuous use.
Key Specifications
- Magnification: 1×
- Dot size: 2 MOA
- Eye relief: Unlimited
- Clear aperture: 23 mm
- Optic-only weight: 185 g
- Weight with QRP2 mount: 357 g
- Battery: 1/3N, 3V lithium
- Battery life: Up to 30,000 hours
- Water resistance: 45 m (150 ft)
- Night vision: Compatible
- Operating temperature: −45°C to +71°C
- Mount: QRP2 mount included with the standard package
Pros
- Long battery life
- Rugged aluminum construction
- Unlimited eye relief
- 2 MOA dot
- Night-vision compatibility
- Strong water resistance
- QRP2 mounting system included
Cons
- Heavier than the Micro T-2
3) Trijicon MRO
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The Trijicon MRO (Miniature Rifle Optic) is a small 1× red-dot with a relatively large 25 mm objective lens and a 2 MOA dot.
It has an infinite eye relief that enables the user to see through the optic without having to move it to an exact distance.
The design is well adapted to the “both eyes open” sight picture, which allows the dot to be overlaid on the scene being viewed.
MRO’s housing is forged 7075 aluminum and waterproof to 30m (100ft). The illumination has eight settings, two of which are night vision and five are daylight settings, plus a super-bright setting.
CR2032 battery is the standard power source for the standard MRO and is listed for up to 5 years of continuous operation at daylight setting 3 under manufacturer-specified test conditions.
Key Specifications
- Magnification: 1×
- Objective lens: 25 mm
- Dot: 2 MOA
- Eye relief: Infinite
- Clear aperture: 20.4 mm
- Weight: 116 g (4.1 oz), without mount
- Dimensions: 66 × 43 × 51 mm
- Battery: CR2032 lithium
- Battery life: Up to 5 years
- Brightness settings: 8
- Adjustment: ½ MOA per click
- Total adjustment range: 70 MOA
- Water resistance: 30 m (100 ft)
Pros
- Large 25 mm objective lens
- Unlimited eye relief
- Compact and relatively lightweight
- Long stated battery life
- Multiple brightness settings
- Night-vision-compatible settings
- Rugged aluminum housing
- Waterproof construction
Cons
- More expensive than many entry-level red dots
4) Trijicon RMR Type 2
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The Trijicon RMR Type 2 (Ruggedized Miniature Reflex) is a compact reflex sight that affords a clear and open sight picture.
Its 3.25 MOA red dot and unlimited eye relief make it possible to view the dot naturally while keeping both eyes open.
Offers a wide field of view and has a multi-coated, tempered glass that is optimized for accurate and sharp colour transmission.
The new RMR Type 2 features an aluminum housing with a protective design. The flexible LED version has eight brightness settings, including night-vision settings.
Operates on a CR2032 battery and is waterproof up to 20m (66ft). The battery-life data are based on usage and brightness, and typical data provided by Trijicon are several years given certain conditions.
Key Specifications
- Magnification: 1×
- Reticle: 3.25 MOA red dot
- Eye relief: Unlimited
- Dimensions: 1.8 × 1.1 × 1.0 inches
- Weight: Approximately 1.2 oz (34 g)
- Battery: CR2032 lithium
- Brightness: 8 adjustable settings plus automatic mode
- Adjustment: 1 MOA per click
- Housing: Forged aluminum
- Water resistance: 20 m (66 ft)
- Night vision: Compatible on appropriate models
Pros
- Very compact and lightweight
- Unlimited eye relief
- Open sight picture suitable for both-eyes-open viewing
- Rugged forged-aluminum construction
- Multiple brightness settings
- Night-vision compatibility
- Waterproof construction
- Widely supported RMR mounting footprint
Cons
- Relatively small sight window
5) Holosun HS510C
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The Holosun HS510C is an open-reflex 1× optic with a wide viewing window to allow a wide sight picture and both eyes open viewing.
It has a Multi-Reticle System (MRS) that lets the user choose from a 2 MOA dot, a 65 MOA circle, or a combination of circle and dot.
The large window and unlimited eye relief are designed to help you easily identify and acquire targets while still seeing what is happening around you.
HS510C features an aluminum body and a titanium guard hood. It has a Solar Failsafe that recharges the battery and Shake Awake that wakes up the optic if it detects motion.
It is powered by a CR2032 battery and, according to the current Holosun specifications, provides up to 50,000 hours of battery life at setting 6.
Also features 10 brightness settings for the day and 2 for the night—both of which are compatible with night vision.
Key Specifications
- Magnification: 1×
- Reticle: 2 MOA dot / 65 MOA circle / circle-dot
- Eye relief: Unlimited
- Parallax: Parallax-free
- Window size: 0.91 × 1.26 inches
- Weight: 4.94 oz (approximately 140 g)
- Battery: CR2032
- Battery life: Up to 50,000 hours at setting 6
- Brightness: 10 daylight + 2 night-vision settings
- Adjustment: 0.5 MOA per click
- Housing: Aluminum with titanium hood
- Water resistance: IP67
- Mount: Integrated quick-detach Picatinny mount
Pros
- Large open viewing window
- Unlimited eye relief
- Multiple reticle options
- Solar Failsafe and Shake Awake
- Long stated battery life
- Lightweight open-reflex design
- Titanium protective hood
- Side-access battery tray
- IP67 waterproof construction
Cons
- Open-emitter design leaves the LED area less enclosed than an enclosed optic
6) Holosun EPS
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The Holosun enclosed-emitter red-dot sight was created to fit into a compact enclosed package with a clear and consistent sight picture.
It has a 2 MOA dot, so it gives a quick aiming point, and the unlimited eye relief means that it can be used at a distance from the optic.
Enclosure keeps the LED protected from environmental factors like rain, dust, and debris. The compact mounting for the sight also lends itself to uses where a small optic footprint is required.
EPS has several electronics features such as Shake Awake, which lights the unit when there is movement, and multiple brightness settings.
It features a battery tray that mounts on the side, which means that the battery can be replaced without removing the optic.
The optic also features an aspheric lens, which is supposed to give a clear and distortion-free sight picture.
Key Specifications
- Magnification: 1×
- Reticle: 2 MOA dot
- Eye relief: Unlimited
- Emitter: Enclosed
- Battery: CR1620
- Battery life: Up to 50,000 hours, depending on setting
- Brightness: Multiple daylight and night-vision settings
- Adjustment: 1 MOA per click
- Water resistance: IP68
- Housing: Aluminum
- Lens: Aspheric glass
- Features: Shake Awake, Super LED
Pros
- Enclosed emitter protects against dust and moisture
- Compact and lightweight
- Unlimited eye relief
- Long battery life
- Side-access battery tray
- Shake Awake technology
- Multiple brightness settings
- Clear sight picture
Cons
- Smaller viewing window than the HS510C
7) Vortex StrikeFire II
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Vortex StrikeFire II is a tube style 1x red-dot sight that offers an easy eye-in-hand position and 100% eye relief.
It features a 2 MOA dot that can be seen with a 30 mm objective lens, enabling it to be used with both eyes open.
Has a 10-level illumination system, with a red dot (standard) and a green dot (on some setups). The brightness can be adjusted to suit different lighting.
Tough aluminum body that is hard anodized and is nitrogen purged and O-ring sealed to resist water and fog. Its fully multi-coated lenses are designed to improve light transmission and provide a clear image.
For the standard configurations, the optic is also attached to a cantilever mount, which allows for easy mounting on compatible optic rails.
Key Specifications
- Magnification: 1×
- Objective lens: 30 mm
- Reticle: 2 MOA red dot
- Eye relief: Unlimited
- Adjustment: 1/2 MOA per click
- Maximum elevation/windage: 100 MOA
- Battery: CR2 lithium
- Illumination: 10 brightness levels
- Length: Approximately 5.6 inches
- Weight: Approximately 7.2 oz
- Construction: Aluminum housing
- Water/Fog resistance: O-ring sealed and nitrogen purged
Pros
- Simple 2 MOA aiming point
- Unlimited eye relief
- Suitable for both-eyes-open viewing
- Multiple brightness settings
- Durable construction
- Fog and water resistant
- Fully multi-coated lenses
- Generally more affordable than premium optics
Cons
- Heavier and larger than compact red-dot designs
Factors To Consider When Choosing Red Dot Sight for Both Eyes Open
There are several factors that can impact the clarity, speed, durability, and overall usability of an optic when using it with both eyes open. The differences discussed above with regard to the Aimpoint Micro T-2 and PRO, Trijicon MRO and RMR Type 2, Holosun HS510C and EPS, and Vortex StrikeFire II are the primary differences to keep in mind.
- Sight Picture and Window Size
The size of the viewing window can make a difference since a larger window can offer an open sight picture. For example, the HS510C by Holosun features a big open-reflex window, and smaller viewing sizes like the Trijicon RMR Type 2. There is a different sight picture with the tube-style optics like the Aimpoint and the Vortex models.
- Reticle and Dot Size
The way in which the reticle is designed will impact the way the aiming point will look. A 2 MOA dot is a popular choice, and the HS510C also has a 65 MOA circle and circle-dot setting. Multi-reticle systems are more flexible than a simple dot, usually giving a clearer sight picture.
- Eye Relief and Parallax
Red dot sights are also known for having unlimited eye relief, which means that you can use both of your eyes to see through them. Another measurement to look at is parallax performance as that impacts the dot’s relationship to the target when the viewing angle shift occurs.
- Battery Life and Power Features
For long battery life, you do not have to replace the battery often. The two Aimpoint Micro T-2 lighting systems and Holosun HS510C are designed for extremely long operating periods. The HS510C includes other features like Solar Failsafe and Shake Awake to offer extra power management capabilities.
- Durability and Weather Resistance
Look for the features of housing, water resistance and temperature ratings. Forged or reinforced aluminum housings, sealed electronics and nitrogen purging can help to withstand harsh environmental conditions.
- Size and Weight
Smaller optics like the Micro T-2 and RMR Type 2 are more compact and lighter than larger optics, which are typically heavier, such as the StrikeFire II.
FAQs
- What is a red dot sight?
A red dot sight is a non-magnifying optical sight that projects an illuminated aiming point onto a lens. Its 1× magnification and unlimited eye relief allow the user to view the sight picture naturally with both eyes open.
- Why are red dot sights suitable for both-eyes-open viewing?
Red dot sights generally provide unlimited eye relief and a simple aiming point. This allows the user to keep both eyes open rather than having to align traditional front and rear sights.
- What dot size is commonly used?
A 2 MOA dot is common among models such as the Aimpoint Micro T-2, Aimpoint PRO, Trijicon MRO, Holosun HS510C, and Vortex StrikeFire II. The Trijicon RMR Type 2 is commonly available with a 3.25 MOA dot.
Final Thoughts
Red dot sights offer a simple optical design that can support a natural sight picture when used with both eyes open.
The Aimpoint Micro T-2, Aimpoint PRO, Trijicon MRO, Trijicon RMR Type 2, Holosun HS510C, Holosun EPS, and Vortex StrikeFire II each have different characteristics in terms of size, window design, reticle options, battery life, durability, and mounting compatibility.
When comparing these sights, it is important to consider the features that match your particular requirements rather than focusing on a single specification.
Understanding the differences between open-reflex, enclosed, and tube-style designs can make it easier to evaluate the available options.
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