Ergotron MX Desk-mounted Monitor Arm - screen size: up to 30"

I bought two of these and can confirm they are good value for the price and sturdy/stable as hell.

However, there some issues:
a) The range of motion is too short, e.g., you really cannot use a 32 inch monitor in portrait mode even in the highest position (I know it says up to 30 inches).
b) The tension cannot be configured properly if you do not meet the minimum recommended weight, so it will not work with a laptop mount/light monitor. It either bobs to the top and cannot stay low, or stays flabby at the bottom and cannot be brought up.

So, you need a <30 inch and >6kg monitor, good luck with that. For reference, a 30 inch Dell Ultrasharp is 6.48 kg (without stand).