Abstract: A device for adjusting a rolling bearing for mutual sliding of mast members for supporting a fork carriage of a fork lift truck includes a threaded coupling between an inner ring of the rolling bearing and a relative support pin, and an actuation member freely rotatable through the support pin and rotatably connected with the inner ring. The actuation member can be maneuvered to rotate the inner ring and vary the axial position of the rolling bearing with respect to the support pin through the threaded coupling.