ARHH, Sorry...I should've been clearer. First, you've got two main types of systems.....night vision and thermal. Night vision amplifies available light whereas thermal systems look for heat. Night vision is a lot cheaper then thermal, but thermal works on a bright night, a dark night and even in the daylight. You can also divide these devices into different categories...weapon sights and "viewers". Obviously, weapon sights have crosshairs in them and are designed to be mounted on a gun. Viewers are designed for "viewing" and are usually monoculars or binoculars. Everyone is familiar with binoculars....monoculars are simply 1/2 of a set of binoculars...you look through one eye instead of two. Since night vision binoculars have two sets of lenses and image intensifiers, they cost about twice as much as monoculars. What you buy depends on what you want to do. Are you looking for something to "look" through or do you want a scope, to mount on your gun, to "shoot" through? I know it's confusing, but we'll get it figured out! LOL.