For the safest operation, your Road Pro needs an arrow board mounted on the back. At 30" x 60", this is largest arrow board that will fit on a Road Pro. It features 25 very bright LED lamps that have integrated auto dimming. Included is a small, user friendly control box that mounts in the operators station. The control box has 12 different patterns and has built in diagnostics that detects failed lamps, low vehicle battery, and short circuit conditions. Visible up to 1 mile.