What is the size (I am too lazy to go and get calipers..)
I did the change on my stem, I believe they are M5x17.5 (possibly M6 but I can't remember off the top of my head). There is a thead over at ww.
The only issue that I had is that there were some convex washers on the original steel bolts that create a flat surface for the bolts to sit on (stem holes have concave shape). But I wasn't able to just slide the washers off the steel bolts.........so i ended up cutting the old bolt heads off. The Ti bolts fit nice and snug now.