ATN started by improving the optical configurations which lowered the F-stop factor and increased optical resolution. By doing this, more light travels through the lens to the tube. More light and better resolution simply means brighter and sharper image. Then ATN added their precision "Red on Green" aiming system, easy push button operation, reticle brightness adjustment and detachable most powerful in the industry 450 mW Infrared Illuminator with dedicated windage and elevation adjustments. The ATN MK 390 Paladin weapon sight is the best 1st Generation scope on the market. The ATN Aries MK 390 easily mounts onto any U.S. standard 7/8" weaver or Picatinny rail.