A kit for a helicopter is described, the helicopter comprising a fuselage and a rotor; the kit comprises at least one device adapted to dampen the vibrations transmitted from the rotor to the fuselage and to be interposed between the fuselage and the rotor; the device, in turn, comprises a first threaded element operatively connectable to the rotor and adapted to, in use, vibrate parallel to a first axis; a second threaded element operatively connectable to the fuselage and operatively connected to the first threaded element so as to, in use, rotationally vibrate about the first axis; and a plurality of threaded rollers, which are screwed on the first and second threaded elements; the rollers being rotatable about their respective second axes parallel to and separate from the first axis with respect to the first and second threaded elements; the rollers are also rotatable about the first axis with respect to the first threaded element and the second threaded element.