We see the world in 3 dimensions. A movie screen, however, is 2 dimensional. In order to see a movie in 3D we need to "fool" our brain, making it believe we are seeing something in 3D that is actually only 2D.This is done by having causing the left eye and right eye to see the same object (image) from a slightly different angle. The left eye must see the left view of an object (visual A) and the right eye the right view of the same object (visual B). Our brain then combines the two visuals, A and B, to create a single 3D image.To form a 3D image, each eye must see only its own visual; that is the left eye visual A and the right eye visual B. If both eyes see both visuals then the brain will not be able to create a 3D image of the object but will create a 2D blurred and out of focus image.To ensure that each eye sees only its own visual, we need to filter out, for one eye, the visual that is meant for the other eye. This is why we need 3D glasses.In 3D glasses, the lens in front of the left eye can filter out visual B which is meant for the right eye, and vice versa. Only properly-designed and manufactured 3D glasses guarantee that each eye sees only "their own visual" - a must to achieve the proper 3D effect and experience.Please note: Premium Polarized 3D glasses ONLY work with circular polarized technology and not with shutter technology or linear polarized systems.Shutter technologies only work with so called "active 3D glasses" which include batteries and need to be electronically linked to the movie screen. They are re-used many times by the cinemas, require washing between uses, look quite clumsy, and are very expensive.