Snellen wall eye chart is the familiar chart with the big letter or symbol at the top and progressively smaller letters at the bottom of the chart down to 20/20 or better. The eye chart assists in measuring visual acuity at a distance of 20 feet away from the viewer. The Snellen chart includes Red and Green color bars for an easy and helpful color vision test. Snellen eye chart Made of Plastic and washable. Perfect for optometrists, students, offices, and schools.