Bottle with a threaded neck having a dispensing device (4,9) for releasing a product inside said bottle, said dispensing device (4, 9) comprising: a) a cap having a female screw screwed onto the threaded neck of said bottle and a substantially and/or generically tubular element, coaxial with said female screw, having a lower end which projects inside the neck of the bottle, said lower end being closed by a bottom wall; b) a hollow piston inserted in said tubular element the hollow piston having an open lower end and a head, the hollow piston defining, together with said bottom wall of said generically tubular element, a chamber containing a product intended to be released in said bottle; characterised in that - said cap comprises a collar joined to the top of said tubular element through a tear-away ring 12 and said head of said hollow piston is suitable for being housed in said collar; - said hollow piston is suitable for breaking through said bottom wall of said cap after the tear-away ring is removed; - the lower end of said hollow piston has a substantially and/or generally inclined profile with respect to the plane defined by said bottom wall; - means (69, 99) are provided which are suitable for stopping the stroke of said hollow piston before a complete detachment of the bottom wall occurs and for preventing said hollow piston from rotating at the end of its stroke. a) a cap having a female screw screwed onto the threaded neck of said bottle and a substantially and/or generically tubular element, coaxial with said female screw, having a lower end which projects inside the neck of the bottle, said lower end being closed by a bottom wall; b) a hollow piston inserted in said tubular element the hollow piston having an open lower end and a head, the hollow piston defining, together with said bottom wall of said generically tubular element, a chamber containing a product intended to be released in said bottle; characterised in that - said cap comprises a collar joined to the top of said tubular element through a tear-away ring 12 and said head of said hollow piston is suitable for being housed in said collar; - said hollow piston is suitable for breaking through said bottom wall of said cap after the tear-away ring is removed; - the lower end of said hollow piston has a substantially and/or generally inclined profile with respect to the plane defined by said bottom wall; - means (69, 99) are provided which are suitable for stopping the stroke of said hollow piston before a complete detachment of the bottom wall occurs and for preventing said hollow piston from rotating at the end of its stroke. - said cap comprises a collar joined to the top of said tubular element through a tear-away ring 12 and said head of said hollow piston is suitable for being housed in said collar; - said hollow piston is suitable for breaking through said bottom wall of said cap after the tear-away ring is removed; - the lower end of said hollow piston has a substantially and/or generally inclined profile with respect to the plane defined by said bottom wall; - means (69, 99) are provided which are suitable for stopping the stroke of said hollow piston before a complete detachment of the bottom wall occurs and for preventing said hollow piston from rotating at the end of its stroke.