An assembly for closing a bottle having a maximum diameter (D), 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 (S) 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 (S) 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 . <EOS>