An assembly for closing a bottle or the like comprising a cage, a closure cap and a sealing nut, wherein: - said cage is substantially cup-shaped and comprises a side wall with an inner surface comprising a first annular relief and a second annular relief spaced so as to form a seat for a collar of the bottle; - said closure cap comprises a head and a shank, wherein said head comprises an upper surface and an opposite annular surface; - said sealing nut is cup-shaped and comprises a side wall; - the inner surface of the side wall of the cage comprises a retaining tooth for retaining in position the head of the closure cap along said annular surface; - said retaining tooth is cantilevered and is inclined with respect to the inner surface of the side wall of the cage; - at said retaining tooth a recess is provided within which the tooth can be retracted, so that the head of the sealing cap can be pushed towards the base of the cage; characterised in that: - the outer surface of the side wall of the cage comprises an annular cavity; and - said side wall of the sealing nut comprises an inner lower protuberance configured to engage with the annular cavity in a preassembly configuration, and - said side wall of the cage comprises a plurality of discrete side walls, each separated by a slit, wherein a discrete side wall is connected to an adjoining discrete side wall with a bridge-piece in the proximity of their free end (102"). - said cage is substantially cup-shaped and comprises a side wall with an inner surface comprising a first annular relief and a second annular relief spaced so as to form a seat for a collar of the bottle; - said closure cap comprises a head and a shank, wherein said head comprises an upper surface and an opposite annular surface; - said sealing nut is cup-shaped and comprises a side wall; - the inner surface of the side wall of the cage comprises a retaining tooth for retaining in position the head of the closure cap along said annular surface; - said retaining tooth is cantilevered and is inclined with respect to the inner surface of the side wall of the cage; - at said retaining tooth a recess is provided within which the tooth can be retracted, so that the head of the sealing cap can be pushed towards the base of the cage; characterised in that: - the outer surface of the side wall of the cage comprises an annular cavity; and - said side wall of the sealing nut comprises an inner lower protuberance configured to engage with the annular cavity in a preassembly configuration, and - said side wall of the cage comprises a plurality of discrete side walls, each separated by a slit, wherein a discrete side wall is connected to an adjoining discrete side wall with a bridge-piece in the proximity of their free end (102"). - the outer surface of the side wall of the cage comprises an annular cavity; and - said side wall of the sealing nut comprises an inner lower protuberance configured to engage with the annular cavity in a preassembly configuration, and - said side wall of the cage comprises a plurality of discrete side walls, each separated by a slit, wherein a discrete side wall is connected to an adjoining discrete side wall with a bridge-piece in the proximity of their free end (102").