They are four piston. After you bead blast, paint and apply the AMG logos they are identical to C32 but are somewhat easier to find. The only difference is that you have to use some washers between the mount and the caliper. For the 345mm C32/C55/CLK500 rotor you can use C32/C55/CLK500 calipers or you can use S600 or CL600 calipers with about $4.00 worth of washers. For the 330mm SRT rotor you can use CL500 or S500 calipers with the same washers to center the caliper over the rotor. The CL500/S500 caliper is the only caliper that I have found that will work with the SRT rotor.

I picked up my custom rear mounts from my machinist last night. Time permiting, I will have the new rear set on this weekend which as mentioned above are 330mm rear SLK55 rotors with S/CL65 calipers. I could have used SLK55 calipers but they are expensive and almost non existent to find. Wait till you guys see the S65 calipers! They look like mini me versions of the front calipers. After upgrading the front brakes the tiny stock n/a rear brakes looked rediculous compared to the front.