Genuine OEM Audi Spark Plug, part number 101905621. This essential engine component is responsible for igniting the compressed air-fuel mixture within the combustion chamber, initiating the power stroke. It screws into the cylinder head, with its tip exposed to the combustion process. Weighing approximately 0.046 kg, this spark plug is engineered for precise heat range and electrode gap. Choosing genuine OEM spark plugs ensures correct thermal characteristics, consistent spark delivery, and optimal combustion efficiency, which is vital for engine power, fuel economy, and emissions control.