Eagle Tree Magnetic (Hall Effects) RPM Sensor with 4 magnets

This is the Eagle Tree Systems magnetic RPM sensor that we recommend for our chassis dyno.  Although it comes with 4 small magnets, don't use them.  We've already installed 2 stronger magnets on the back side of the idler spur gear on our dyno.  When installing underneath the idler spur gear, remember that the sensor is directional.  Install it so the wide part is facing the gear.