The LI-20 is a prismatic panel with a 1/8 in. square base male conical prism placed parallel and perpendicular to the length and width of the panel. The LI-20 is our newest specification panel, it offers excellent brightness control and a soft surface appearance. Available in acrylic only. Recommended thickness is .140 in. for 2 x 4 ft. panels and .165 in. for 4 x 4 ft. panels.