solid, only small flat building, hence quite a game in the bottom horizontal level locking. if the screw is a little tight against the bottom pivot a clearance of 1.5 mm, and if a bit is locked screw, there is little turning laterally. very annoying when même.Dommage because the rest is good. I recommend putting a bit more and have something really correct. more I sent a message of discontent through Amazon, but no response, so brand Pendulum ball to avoid.