Thermal balancing - Initial values taken for adjustment

Do these square bars actually have a uniform edge length? What should I look for at the hardware store if I don’t want to keep twisting with the pliers forever?

I can adjust our manifold with a completely normal standard 0815 vent key. So the kind that is also used for radiators.

Hello everyone. I have now made the first adjustments. In my opinion, something is not right. I have made a complete turn to the left in the bedroom and the dressing room upstairs. I have also noticed that none of the distributors can be turned to the right. In my opinion, the end position has already been reached here. I have attached a picture for this. There you can see that when I turn the regulator to the left, the entire brass part screws down a bit. I cannot turn to the right to increase the flow because the brass part already hits the top. I hope you know what I mean. For example, I have noticed downstairs that there is hardly any flow in the hallway and utility room downstairs. There, the regulator is below 0.5. No idea if these circuits are even still open.

Do the red covers possibly still need to be turned? Although I wouldn't know what that should trigger. The caps have no connection to any mechanics.

It would be advantageous to know who the manufacturer of the valve inserts is, then one could say exactly what needs to be done.

Yes, I would like to know that too. We had to have the plumbing work completed by another company. Therefore, I can no longer ask the plumber. There is nothing on the system itself. According to the offer from G.U.T., the actuators are.