you can use a normal deep well socket, break the plugs loose then use a piece of rubber hose (like a gas line) feed it into the spark plug hole and push it onto the connector of the plug, Turn the hose to unthread the plug and pull it out.
I've found the tool in my local car spares, its classed as a 10mm (16mm euro), I've measured the spark plug AF (across flats) & that comes out at 15.65mm.
I suggest if you have concerns ask for the socket when you buy your new plugs.
Not sure if they are all the same for all A4's
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