Ordering by number: this is 470W117390, the Chicago Pneumatic washer. It sits under the fastener to preserve the mating face and hold tension in a joint that vibrates constantly.

If you are working from a machine rather than a part number, start at the parts diagram hub, or send us the model and serial and we will match it. Machines themselves are on the CP tool catalog. Denver stock, with same-day shipment on in-stock orders in by 4 PM ET.

• Part number: 470W117390
• Manufacturer: Chicago Pneumatic
• Crowder SKU: CP-470W117390