Basically prisms are located inside binoculars that act like mirrors. It is a eflectivecoating on glass that
bends and refracts light to bring the subjects you are looking at to your eyes. The BAK-4 prism is made
of a high quality glass and produces sharp images and good edge to edge sharpness. . Generally, higher
quality binoculars will use BAK-4 prisms in the construction process. But phase coated prisms take it one
step further, the coating process enhances the resolution and contrast of images coming through the
binocular and are generally applied only on more expensive binoculars.