Something wobbly / Total fine

I bought this office chair, because the well-known variant of this chair (Topstar OP20QG20) has no height-adjustable armrests. My plan was to then height-adjustable to fit the armrests TOPSTAR 7096 U2 to Express 06-04 / 06-10 Express / Express 06-11 it. This also works beautifully.

Positives:
-Very Comfortable even after prolonged sitting.
-Are (Still) no noises.
-Easy Installation.

Criticisms:
- The chair is a little shaky with me. Both the seat and the backrest are somehow not permanently mounted to 100%.
- The backrest is continuously adjustable in height. For me personally, the distance from one stage to the next is too large.
- Unfortunately, you can mount the armrest in a single width. I would have wished there more scope to customize the armrests to the needs of thin and less thin people can.

Overall okay. For the price I would have liked, however, a more stable design that does not wobble! Because the chair is otherwise very comfortable, I forgive 4/5 stars.