I want to preface this by saying that I believe in the buy it for life philosophy, since buying cheap gear has burned me many times in the past. I chose the Gravity desk stands over the cheaper millenium and fun generation stands which are basically half the price.
These stands are sturdy and have a good heft to them. Where the stem connects to the base is just metal on metal which is not the best solution imho. The knobs and adjustments feel ok, but there is some play in the top plate after tightening. This isn't an issue once you put your speakers/moniters on them, but it's kind of weird to see. To swivel the stands you have to take your speakers off because otherwise they'll drop down if you try to untighten the adjustment knob. I feel like they could've done this better by adding a rotating plate (on bearings) that adjusted separately from the main adjustment.
There's a thin piece of memory foam on the top plate and despite the stands taking away a lot of vibrations, they still allowed a lot to reach my desk. Use some foam speaker stands on top and some cheap cork coasters (2euro at Woolworth) on the feet and your vibration woes are completely gone.
On my initial order one of the stands was broken, it took a lot of force to tighten the main knob and it still wouldn't hold my 5kg monitors up properly. Luckily Thomann quickly exchanged it and the replacement was working properly. Still, for a German made product which prides itself on craftsmanship these are silly things to let through and should've easily been caught in QC. Still, compared to the other adjustable stands this is definitely the way to go.