Ordering by number: this is 4700W65007, cross-referenced to 0663211600, the Chicago Pneumatic O-Ring. Its job is to hold the pressure boundary between two mating faces; a hardened or nicked seal shows up as lost power and a damp housing well before anything else fails.

Matching it to a machine? Send us the model and serial and we will confirm the fit, or work back from the full diagram library. Complete tools are on the CP tool catalog. Denver stock, with same-day shipment on in-stock orders in by 4 PM ET.

• Part number: 4700W65007
• Also listed as: 0663211600
• Manufacturer: Chicago Pneumatic
• Crowder SKU: CP-4700W65007