Mini reflex sights came to be because of EoTech's innovation in reflex sights. The company's 500 series of Heads Up Weapons Sights are so tough they even function if the screen is cracked. The drawback is these sights seem large compared to other optics.
To combat this problem, EoTech redesigned the 500 Series, mounting the batteries horizontally to the screen instead of vertically. The new XPS Series is the result. This shorter sight gives you room enough to also mount night vision, lasers, and magnifiers with it on the rails of your weapon.
I had been using the XPS2-0, which is not NVD capable, so I was happy to start using the XPS3-0, which is. From the time I opened the box I was hooked. A smaller, lighter version of my time-proven 552, the XPS2-0 sight is very much like its larger sibling; it's a keeper.
Insight Technology and Trijicon took this reflex technology and shrank it down. One advantage of the mini-holographic scopes is they can be mounted on telescopic rifle scopes. You can find numerous scope mounts that allow you to mount Insight's MRDS or Trijicon's RMR on your scope, rail, or to the scope rings. This allows a precision marksman to use his rifle for CQB should he suddenly find himself in that situation, or it gives you a backup sight should your primary sighting system fail.
Another advantage of the miniature reflex sights is their toughness. Both of these sights are waterproof to beyond 60 feet and will run nearly forever on one battery. Should the battery die on the Trijicon RMR, fear not; the dot will glow thanks to its dual power fiber optic.