This product is a genuine Fadal OEM pulley, which means it's an authentic part made by Fadal. It's a pulley used in the spindle belt drive system, specifically attached to the spindle motor. In the past, early VMC machines used six belts with this pulley before switching to a newer design called the Serpentine belt. https://itscnc.com/spindle-motor-pulley-6-belt-non-coolant-thru.html