So much for the better. The weak point of the chair is the connection between the seat and backrest, the latter is screwed centrally under the seat. If you frequently use the tilt function as in my case, while load backrest, are the tube in the backrest above the screw gradually the rest flexes after some time slowly getting further back, what initially "rebounds" by stepping up the rest noticeable makes and later leads to the the rest ever tilts backwards. The toward the end forcibly necessary bending back speeds up the process, of course, even more, in the last instance to the Rückenlehn yields completely and tears off.
Conclusion: This gives here a very comfortable chair for fatigue-free work, unfortunately, with a permanently inadequate stable backrest when using the tilt function. Chair where the backrest can be bolted on the arm rests, here offer a lot more stability.