I did not measure it.
I would have to disassemble it to take measurements.
I'd rather fly it right now.
The head ships with a 550 DFC main mast.
You can see (in the pictures) that the head block has 2 jesus bolt holes.
And, the 550 DFC main mast has 2 jesus bolt holes.
When the head is fully seated on the 550 main mast, all the jesus bolt holes line up within 1mm and the bolts slide in.
I used the Align Trex 600 nitro main mast.
This has 1 jesus bolt hole.
I lined up the lowest jesus bolt hole on the head block with the existing hole on the 600N DFC main mast.
This was the best fit in terms of swash height, clearance and almost "drop in" head replacement.
But, at that point, the head was not fully seated by a long shot.
I estimate that if the mast was about 10mm longer on top, it would be a better fit.
If I lined up the upper jesus bolt hole on the head block with the existing jesus bolt hole on the main mast, the head was almost fully seated, but the main grips were too low and would scrape the swash anti-torque guide and the swash links would have had to be replaced with 10mm shorter links.
After I lined up the lower jesus bolt hole in the head black with the existing hole in the 600N DFC main mast, I marked the upper the location on the main mast where the upper jesus bolt hole was, and drilled the main mast to match.
The two new holes are about 5mm below the top of the main mast.
We will see if it hold up.
Believe 1/2 of what you see and none of what you hear.
Fake News will be the downfall of our Republic!