These “arms” are surprisingly good. The clamp on the desk has dual screws so the attachment point to your desk is not going to move. The height adjustment can only occur at the main post too so there is no wriggle-jiggle of any screen you attach, or laptop you place on the tray.
If you're not needing to raise your laptop or screen up and down continuously (and I don't know who might, but is a feature of other mounts, drives my son crazy) and you just want to get some desk space clear and put your gear in the air, then this is a good option. Might buy another for my daughter's setup, and I'm thinking another single for myself.
There are a few down sides (losing the 5star rating): 1: The side-clamps on the tray which will hold onto your laptop for dear-life (they are strong) are hopeless because they cover up the ports you need on the side of your laptop – both sides. Luckily you can peel back the rubber mat on the tray to expose 6 screws that you can undo to take the clamps off. Clamps are not needed, not even in an earthquake. The arms hold the tray securely enough alone for your laptop to be perfectly safe without the clamps.
2: The main post is about 1–2 cms too short for me (I'm 183cm tall) so I can't quite get that dead-ahead eyeball to top of screen line for perfect posture. I'm not suffering in any way, but I do notice it. It might lead to some neck cramps if you're taller than me tho'.
3: Instructions are as hopeless as most are, printed on a tiny piece of paper with teeny numbers and arrows and such. If you're good with kit-set furniture and/or other such assembly, you'll have no problem.
4: More on the instructions, the specs say the clamp can get around a 7cm (or less) thick bench. As packed the clamp is set up for about no more than 5cm – you need to expand the clamp releasing 4 screws and re-setting them in the extra screw holes to get the full 7cm. There is nothing in the instructions hinting that you can do this.