I've used these on my motorcycles, which makes replacing brake fluid much easier. I can't find ones for an A6 . Any idea the dimensions of the bleeder valve on a C5 A6.
They have a check valve built in to keep the air from returning in when loosened. Makes bleeding brakes a one man operation.

 

I was able to find the answer to my own question.

Front....SB1010S
Rear.....SB1010S

They are definitely worth checking out if you plan to bleed your brakes.