This aid allows to exercise a coordinated movement of upper limbs, or the movement by one hand only, rotating one or more metal balls inside a plastic container for an unlimited time or decided by the assistant. The rotation of the spheres can be varied according to the movement of the arms; the speed of the balls can be remarkable as the cover does not allow them to come out. The aid can also be used simultaneously by two people so that the movement of the spheres is guaranteed by both.