The AEM Dyno-Shaft On-Vehicle Dynamometer is a true on-vehicle dynamometer system that measures Torque and RPM while you drive to deliver Horsepower numbers in real time. It measures Horsepower, Torque and RPM as accurately as the most respected dynamometers, with the advantage of being able to gather this data in real-world conditions. The Dyno-Shaft Pro Series is designed for professional racers and users who have ultra-high stress applications and are already using or require a CNC machined, Chrome Moly slip yoke. If your vehicle can utilize a cast-iron slip yoke, the Sportsman Series Dyno-Shaft is available at a much lower cost and delivers the same performance for applications that do not require the strength of a Chrome Moly slip yoke. The Dyno-Shaft is compatible with the AEM AQ-1 Datalogger as well as any Series-2 EMS.