When I purchased my 2002 S6 Avant two months ago, the passenger side outer axle boot had a small tear in it. As the S6 still had it's original axles in it with close to 97K miles , I just ordered a pair and installed them both at the same time , even though neither original axle was making any noise. (for peace of mind). For $200.00 a side, I think it is a bargain. After installing the new axle, you just send them your old axle (core) in the same box with a prepaid label. Very professional company to do business with, I've been extremely pleased. Good Luck, regards, Paul