The standard size of Z4M/e46 CSL discs is 345mm x 28mm front and 328mm x 20mm rear.miffin said:The standard size of a z4ms discs is 350 front and 330 rear and an m3 has 330 front and rear
where the increased stoping power comes from with this kit is the standard calipers as one piston the brembos as 4 and the pad surface area is a lot bigger
I hope this helps