However, it cracked when tightening a scvhraube already screwed further perk up, screw in two out of four cracked it. then my son-30kg sample sat and played a few songs on the piano. it crunched. apparently the stool of stress was not up by a 8 year old, at least two of the feet were loose afterwards, when tightening the screw broke then the thread (the thing in which the screw was turned pure) out. A closer look at the damage I realized then that one of the crossbar of the stool scaffold was also broken and a screw in the stool scaffold (ie not by those who are purely turns as user itself) loosely sat and that was splintered wood around.
Now my son is yet again on a normal chair and the piano stool can stay where he wants.