Piston collar size

[SamW]

Hi,

My brake caliper in front is sticking so I'm replacing the whole unit plus the attached brake hose. When looking for the correct part, there seems to be two variations, one with a piston collar of 6,0 mm and other with 9,6 mm. It's seems hard to find precise information about this and I'm not sure which size my car has. Or does it even matter that much which one I choose if I'm replacing the whole caliper anyway? I read somewhere that they changed the sizing in 11/05, mine is 09/03.