Most reflex red dot sights are of the open type, meaning that the light-emitting diode (LED) and the interior of the objective lens are exposed to the elements. Only a few red dot sights in this category have these two parts sealed (Steiner MRS, Holosun 512, etc.)
The objective lens is curved so that the beam emitted by the LED can reflect the user's eye in front of the device regardless of its position. The coatings applied to the lens reflect only the colour of the emitted beam, all the other colours pass through the lens. The most common colour is, of course, red. Nevertheless, some companies have started manufacturing green and gold dot sight because many people have problems seeing the red colour.
Holosun Reflex HS407C-RD V2 reflex sight
Reflex dot sight is parallax free. The majority of them are small and compact (some reflex dot sights designed for AR-platforms are bigger and bulkier). There are all sorts of mounting footprints when it comes to this category. The most popular is Docter/Noblex footprint profile. More information about the footprints on the red dot sight is available here.
These red dot sights must be small and compact so that they fit on a handgun. Pistol users generally prefer bigger dot projections (6 MOA –7 MOA) as it allows for quick target acquisition. These sights can also be used on rifles, but most rifle users opt for smaller dot projections (2 MOA –3.5 MOA). Handgun reflex sight withstands powerful recoil. Some modern pistols are designed so that a particular red dot sight footprint matches the mounting surface of the pistol perfectly (they are optic-ready).
Even though some reflex sights can be used on handguns and rifles, rifle-oriented reflex sight is generally bigger. They are equipped with a large objective lens and often supplied with a Picatinny mount.
The dot size in reflex sight is associated with the field of use. Dot sizes 1 MOA –4 MOA are great for rifles as they provide more accuracy at distances up to 75 m. Dot sizes 4 MOA–10 MOA are a perfect choice for pistols since they allow the shooter to acquire the target faster. They provide sufficient accuracy at a distance of up to 40 m.
All dot sights operate at around 1x magnification. For this reason, the user can look through with both eyes open which add to the comfort and simplicity of use. Even though the shooter is looking through the lens, he or she remains aware of the surroundings (the peripheral vision is not affected). Reflex sight boasts unlimited eye relief and unlimited eye box (the dot is always on target as long as you see it, regardless of the eye position, allowing for quick target acquisition. In comparison to tube dot sight, reflex dot sight generally provides a less obstructed field of view (the frame around the lens is thinner).
Every reflex sight is a red dot (or a green dot, or a gold dot, depends on the colour of the emitted beam) – reflex sight is a subcategory of a red dot. Most people, however, think about tube sight when they hear the term 'red dot'.
That depends on the dot size. Reflex sight designed for rifle use (1 MOA –4 MOA dot size) provides considerable accuracy up to 75 m.
Reflex sight designed for pistol use (4 MOA –10 MOA dot size) is accurate at up to 40 m. The accuracy is increased if the dot is paired with a magnifier.
These are designed by the following companies: