Master cylinder diameter of HFX-Mag brakes

Mar 1, 2004
Montreal Area
Hey there, I've got these 2005 HFX-Mags lying around, and here's what I wanna do.

I wanna take the hayes levers and put them on my Grimeca calipers. Now, I need to know the diameter of the HFX-Mag M/C to see if it can work.

Anyone know the answer to this ?