OES

OES or Original Equipment Supplier, refers to manufacturers of Volvo Blue Box parts that Volvo has contracted out to. For example, Volvo does not make spark plugs itself, but instead gets spark plugs meeting their specifications from ignition specialists like Bosch and NGK.

Where you see a part marked OES, it means it's coming from the same source that supplies Volvo OE products. You get the peace-of-mind of a Genuine Volvo part, without the huge price tag.