7mm allen head. If they are stuck then I would torch the heck out of them and then try again. Nothing worse than rounding off an allen key'd caliper pin... Last time that happened to me I had to break out the acetylene torch and basically make the thing red before going at it with a huge set of vise grips and backing it out... The good news is, you can remove the whole caliper/bracket as a unit if need be, just a bit of a pain and you'll have to unhook the break line to work on it in some other location which means you need to bleed them all when you put it back on. Probably should bleed them all anyway though.