If the standard flywheel is removed to fit either a lightened flywheel or a race type clutch/ flywheel assembly you will need to fit this counter balance weight onto the back of your engine to mount your new light flywheel as the flywheel attachment is completely different, necessitating this weight to be fitted.

Disclaimer/ Whist not always necessary, we would always advise an engine balance to go with a weight change on the rear of the engine due to potential bearing damage this "could" cause.