A kit (1) for a helicopter (2) is described, the helicopter (2) comprising a fuselage (3) and a rotor (4); the kit (1) comprises at least one device (15) adapted to dampen the vibrations transmitted from the rotor (4) to the fuselage (2) and to be interposed between the fuselage (2) and the rotor (4); the device (15), in turn, comprises a first threaded element (21; 20) operatively connectable to the rotor (4) and adapted to, in use, vibrate parallel to a first axis (B); a second threaded element (20; 21) operatively connectable to the fuselage (4) and operatively connected to the first threaded element (21; 20) so as to, in use, rotationally vibrate about the first axis (B); and a plurality of threaded rollers (22), which are screwed on the first and second threaded elements (21, 20; 20, 21); the rollers (22) being rotatable about their respective second axes (C) parallel to and separate from the first axis (B) with respect to the first and second threaded elements (21, 20); the rollers (22) are also rotatable about the first axis (B) with respect to the first threaded element (21; 20) and the second threaded element (20; 21).