If the diameter of the hole on the desk is greater than 90mm, a clamp style mount is recommended.
A clamp-style desk mount is recommended when you want the flexibility to move the position later. Here are the considerations:
Installation at the back of the desk:
1. There should be more than 5 cm of space between the edge of the desk and
the wall behind it.
2. Be mindful of the support specifications for the desk clamp. The BenQ Ergo
Arm clamp can accommodate a tabletop thickness of 1.7 to 5 cm (with a
reinforcement plate, it supports 1.2 to 4.5 cm).
3. There should be a clearance of 5 cm under the desk to allow for proper
clamping.