Yea like tuffty said just get them from Audi, they'll be the latest ones as they did modify them several times back in the day when the vag group had thousands of cars off the road due to failures of the earlier ones, at one stage they listed the part numbers of the ones guilty of failure and advise to replace any old types ones weather they had failled or not. You'll also get a decent parts warranty with the genuine was that you may or may not get with a cheaper alternative.
Ewan.