I was able to do some research and according to the manufacturer the height of the arm is 883mm and the outer height of the clamp is 105mm. This means that it protrudes 88.3cm upwards from the surface of the table top. I have requested that we correct the information.
I was able to check it and unfortunately the manufacturer does not specify what the diameter of the rod is. Below is a link to the manufacturer's site. There it has a technical drawing of the product if it helps.
Manufacturer's page DIGITUS Universal Dual Monitor Mount, Vertical
Load 8kg per monitor.
I think because 8kg in total is impossible, I've had it for 2 weeks now, I have a 27. And 32 ... and it holds superbly well, it's really good quality.