Features: 1.Rear Window Speed Display: Shows driving speed on the car rear window, to remind the driver behind, to keep safety driving distance and avoid collision. 2.Design: The speed display range is 0?199km/h, with high accuracy time display, designed with black panel and green digit, which is clear, visible for the driver behind. 3.Double Sided: This display can be used as an internal speed display when mounted on the front windshield, and the speed display on the back of it can be used as exterior window speed display. 4.Application: The windshield speedometer display is applicable for car, SUV, school bus, truck and other kinds of special vehicle, the large size design is eye catching. 5.Installation: Plug and play, non destructive installation with suction cups, and the power supply can be connected to the 11.5V?30V power supply with the cigarette lighter plug. Specification: Item Type: Car HUD Display Material: PC Power Supply: 11.5V-30V Speed Range: 0-199km/h Working Environment: -40 C - +80 C Time Error: Less than 1minute Fitment: Suitable for cars, trucks, buses Note: This product is powered by 11.5V~30V, please do not use power supply above 30V.