An assembly for closing a bottle having a maximum diameter, the assembly comprising a cage, a closing stopper and a ring nut, wherein: a) said cage is substantially cup-shaped and comprises a side wall with an inner surface comprising a bead and a lip spaced in such a way as to form a seat for a collar of the bottle; b) said closing stopper comprises a head, wherein said head comprises an upper surface and a lower surface; c) said ring nut is cup-shaped and comprises a side wall; d) the inner surface of the side wall of the cage comprises a retaining tooth for retaining in position the head of the closing stopper at said lower surface; e) said retaining tooth projects cantilevered from the inner surface of the side wall of the cage; f) the outer surface of the side wall of the cage comprises an annular cavity; g) said side wall of the ring nut comprises an inner lower projection or knee configured so as to engage the annular cavity in a preassembly configuration; characterized in that h) the side wall of the cage comprises a plurality of windows and a plurality of slits, wherein each slit is situated between two windows, and each of said windows comprises a tongue connected to a portion of the lower edge of the window along a hinge line, the slits are open at the free edge of the cage and extend beyond the hinge line; i) the lip is formed at the free end of each tongue; j) each tongue comprises a step configured for acting as a stop for the knee of the ring nut; k) each tongue is elastically rotatable about the hinge line; and l) each tongue comprises a rounded head so that, during assembly, the engaging tongues can rotate about the hinge line without the outer diameter of the sealing assembly exceeds the maximum diameter of the bottle. a) said cage is substantially cup-shaped and comprises a side wall with an inner surface comprising a bead and a lip spaced in such a way as to form a seat for a collar of the bottle; b) said closing stopper comprises a head, wherein said head comprises an upper surface and a lower surface; c) said ring nut is cup-shaped and comprises a side wall; d) the inner surface of the side wall of the cage comprises a retaining tooth for retaining in position the head of the closing stopper at said lower surface; e) said retaining tooth projects cantilevered from the inner surface of the side wall of the cage; f) the outer surface of the side wall of the cage comprises an annular cavity; g) said side wall of the ring nut comprises an inner lower projection or knee configured so as to engage the annular cavity in a preassembly configuration; characterized in that h) the side wall of the cage comprises a plurality of windows and a plurality of slits, wherein each slit is situated between two windows, and each of said windows comprises a tongue connected to a portion of the lower edge of the window along a hinge line, the slits are open at the free edge of the cage and extend beyond the hinge line; i) the lip is formed at the free end of each tongue; j) each tongue comprises a step configured for acting as a stop for the knee of the ring nut; k) each tongue is elastically rotatable about the hinge line; and l) each tongue comprises a rounded head so that, during assembly, the engaging tongues can rotate about the hinge line without the outer diameter of the sealing assembly exceeds the maximum diameter of the bottle.