This product is a NOS OEM 1966-1972 Chevy 10 Bolt Pinion Shaft Bearing Spacer made by GM. It is a crush collar and is designed for placement on the rear pinion of a vehicle. Specifically, it is a genuine OE/OEM part number 3954478, providing a high-quality and authentic solution for maintaining or repairing the differential in a Chevy truck or vehicle.