Injector seals or washers are located either around the shaft of the injector or a washer above the nozzle. Injectors will disperse fuel at very high pressure and worn seals will be come evident very quickly resulting in a leaking injector. Many describe this as "Black Death" especially amongst Mercedes diesel engines. A deposit of solid carbon will build up around the injector top, making it almost impossible to remove the injector. If you cannot remove the injector, you must take it to a specialist that knows how to remove the injector properly without causing damage to the cylinder head. 
Injector seal & washer supplier
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