The bottle has a connecting ring (2) fixing a nipple in an opening of a flask. The ring has a locking piece (3) provided with locking elements cooperated with corresponding cylindrical lugs of a cylindrical neck of the bottle. Each locking element is movable with respect to the ring so as to occupy locking and unlocking positions, when the ring is placed on the flask. The locking element cooperates with the corresponding lug of the flask to fix the ring on the flask, in the locking position, and the locking element allows withdrawal of the ring from the flask, in the unlocking position.
