SHIFT OF 12 FEBRUARY 2015:
The arm is out of order, I will used it for a few photo shoots, in conditions well below what is recommended by the manufacturer. I think of a manufacturing defect (impossible to unlock the joints using the clamp handle means a "clack" metal). This "bed was present from the beginning but did not prevent the operation of the arm. Then he dropped me without reason when I was making a position adjustment. Really disappointed for the Manfrotto fortunately Amazon replaces me free in the part of the contractual guarantee. Hopefully I will not have the same problems with the replacement! Stay tuned.