B6 & B7 S4, solid brushed aluminium mirrors, can be folding and the same shape as standard.
B7 RS4, solid brushed aluminium "AERO" mirrors as standard (RS4 only), folding was available but in body colour standard only. AERO versions are not available in folding option. Very rare to find an RS4 with body colour folding mirrors, seen them on US cars loads, only ever seen 2 in the UK. The "AERO" mirrors are part of the RS4 "look" just like an M3 also had AERO mirrors.
Note: Very expensive to replace and all brushed aluminium, not chrome and technically not matt either. There are nasty crome covers avaialbe and they are horrid, OEM is the best thing. As you can see from my photo below, mine look shiny, they sort of are as this pic was 20 mins after the car had been detailed but they are more satin than shiny.
I have a B6 S4 and the mirrors are a quality item, cast from aluminium and you can polish scratches out of them, even deep ones.
Sorry for the nerdy info, lol