These glasses allow the wearer to perceive 2-dimensional images in 3 dimensions! Through selective refraction the transparent lenses in the Chromadepth glasses change the perceived depth of different colors. When looking through Chromadepth glasses, for example, anything printed in the color red appears to move toward you and off the face of the paper (or screen). Blue appears to move back behind the paper. By selecting your colors carefully, it is possible to create an entire 3-dimensional image. Colors used with the overhead projector work well too! Sold in packages of 10.