Each Audi spark plug is specifically made for the engine it is placed in to maximize the efficiency of triggering the explosion in your engines combustion chamber. This is where the power of your Audi is generated that propels you down the road. Over the years of development of the internal combustion engine, new technologies have been applied to all areas of your car including the all important spark plug. This includes the use of different types of metals on the electrode of your Audi spark plug to include platinum and iridium. The number of posts at the electrode can also vary for the spark plug used on your Audi. There is the traditional one or you can have two in a V shape. There is also the new quad version which as 4 posts evenly distributed around the end of the electrode. The spark from the plug is one of the key places all mechanics are told to check on an engine that is either not running or running poorly. To test this component on your Audi all you need to do is to remove the spark plug from its place in the engine and plug it back into the wire. By placing the threaded portion of the plug against a metal surface, a ground is established. When the engine is then turned over, a blue spark should be seen from the electrode. If by chance no spark is seen, then the ignition system on your vehicle has a problem and a qualified mechanics should be consulted. If you are changing the spark plugs yourself one major word of caution should always be heeded. The spark is generated from the tip to the electrode thru the hollow ceramic chamber of the plug. If the plug is dropped and a crack develops on the plug, this part will not function. Whatever you do don't drop one when changing them on your engine.