im looking to buy new rotors since ive shaved them down for the last time but i dont know what size to get since they come in 3 different sizes for an 01 a6 2.7t..16" wheel....4 pad front caliper....they come in 288..312..321mm? So how do i know which size to get?

 

You are gonna have the 321mm rotors on the front of that car. I got mine from this site. Check the linkhttp://www.germanpartsonline.com/catalog.html

this should help. It will show you how to check the build code.
Good luck

 

321mm

 

Now that i have which size they are now i need to know what type of clips the front pads use...also what would be a good kind to get?

 

you may or may not have the 321mm, check to make sure that you have the Lucas/Girling HP2 calipers. These calipers use an 8 pad set. Or 4 per caliper. If you do have the HP2 calip[ers then the 321mm are your rotor sizes. Some A6 2.7t came with the ATE brake system which had smaller rotors ( I believe the 312mm)

 

I have the 8 pad set...4 per caliper