If you have the actual 345mm/ C32/CLK55/SLK55 Front four pot calipers , NO washers are needed. the rear 4 pot/ 330mm SLK55/CLK55/CLK63 rear calipers also will not need any washers, but you will need a longer set of bolts to secure the caliper . washers will be needed for the w220/w215 chassis calipers, for example the S430 RWD Sport use a 330mm rotor , with these calipers you can run the SRT6 Rotor. the 2001/02 S55 have a 345MM rotor, with these use the C32 rotor and washer spaced four pot calipers. the w211 calipers also need washers. the rarest calipers are the C320/SLK350 sport calipers, they both run a 330mm rotor and are direct bolt on with the SRT 330 rotor. Hope this Helps.