Jaspers 170-4-120B

Value for money, for sure. High quality materials and easy to assemble. All the connectors are in the right place. You just need to look closely (and think) before you put the tubes at the correct locations. I've added casters to move the rack around in my studio a bit. That hardly impacted the stability. I now have a wall of synths and a clean desk again.
The out-of-the-box setup offers a lot of space. So far I've not had to adjust the height or depth of the rows. I've only tuned the angles to get better access to some of the synths. The 40cm holders are wide enough to also hold a shelve on which you can position multiple smaller synths (in my case some Dreadboxes and a Minitaur), in 2 dimensions. A very efficient use of space.

Fully recommended. I have this set up as a 6 tier, wheeled, stand. Perfect for my vintage synths.

I bought the 4 tier stand with the intention of adding two more extension bars (also purchased from Thomann). Assembly requires some forethought, but is simple enough as critical pieces are marked. The instructions are not particularly helpful, but common sense will prevail.

The brackets are notched and fit in to locking 'wheels' on each tier, to physically stop the tubes from rotating, by locking them in to the connector that ties the cross bars to the uprights. That is a great design feature.

Because I changed the format of the stand slightly, I was able to use a 'spare' long tube to brace the middle-back of the stand.

And, in my case, I unscrewed the 10mm diameter threaded levelling 'feet' and replaced with 4 double rubber wheeled casters. (I reused the levelling feet bolts to affix the casters, though I had to hacksaw off the plastic feet as they were too wide for the caster, and were attached to bolts using permanent unremovable screw fittings)

The result is a stable and fully mobile 6 tier rack.