The MSP678 Magnetic Speed Pickup Sensor is designed to detect engine speed by sensing when ferrous materials, like ring gear teeth, pass its tip. It generates electrical impulses proportional to engine speed, which are sent to the speed control unit. It has a durable stainless steel construction, operates between -54°C and 107°C, and can handle harsh environments. The sensor has a 5/8-18 UNF-2A threaded body, a 123mm (4.86 inches) length.