Auto Meter 3900 Sport-Comp Monster Tachometer Traditional incandescent lighting illuminates the front of the dial 12 and 16 volt compatible, well-suited with nearly every street car or race car electrical system Auto Meters race proven air-core electric tachometers provide quick and accurate readings with a needle so responsive it can go from 0 - full scale in 333 milliseconds Compatible with 1 - 4 pulse ignition signals (2-8 cylinder engines) with points, electronic, and most 12V high-performance racing ignitions.