How does it work? It senses magnet signal change when vehicle original alternator is running, then then output 9v pulse for all types of Tachometer/RPM Gauge Easy Installation, no breaking cable, no need CANBUS/OBD Output TACH ratio: 4 pulses/round IP67 Waterproof Mini Size with Play & Plug design Power supply: 9-36V DC Style: Suitable for gasoline and crude oil engines Suitable for gasoline engines Material:ABS plastic colour:Black Package Contents: 1 * speed sensor Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm. ZCL