A closure assembly comprising: - a spout having a spout body that is injection moulded of plastic material, said spout body having, above a seal portion, a tubular neck, wherein a product passage extends through the spout seal portion and the neck of the spout, said tubular neck having a vertical main axis and forming a mouth at a top end of said product passage, said neck having an exterior side; - a rotational cap that is injection moulded of plastic material and that is secured on or is to be secured on said neck of the spout in a closed position of the cap on said neck such that the cap seals the product passage, and the cap - for removal of the cap from the neck of the spout by a user to open the product passage - being adapted to be manually rotated from the closed position in an opening direction (γ); wherein the cap comprises a top wall and a downward depending skirt, said skirt having an interior side, an exterior side, and a lower edge remote from the top wall, wherein the exterior side of the neck and the interior side of the skirt have cooperating rotational connection members, preferably first and second screw threads (16, 23) on said neck and skirt respectively, wherein the cap has two diametrically opposite wing parts, which are integrally moulded of plastic material and extend in a vertical plane outward from said skirt in a lateral direction over a wing part length, characterized in that each wing part has a base portion embodied as a wing panel and an adjoining top portion with two diverging top protrusions that extend upward from the base portion and diverge from one another defining a Y-shaped vertical cross-section of the wing part together with the base portion. - a spout having a spout body that is injection moulded of plastic material, said spout body having, above a seal portion, a tubular neck, wherein a product passage extends through the spout seal portion and the neck of the spout, said tubular neck having a vertical main axis and forming a mouth at a top end of said product passage, said neck having an exterior side; - a rotational cap that is injection moulded of plastic material and that is secured on or is to be secured on said neck of the spout in a closed position of the cap on said neck such that the cap seals the product passage, and the cap - for removal of the cap from the neck of the spout by a user to open the product passage - being adapted to be manually rotated from the closed position in an opening direction (γ); wherein the cap comprises a top wall and a downward depending skirt, said skirt having an interior side, an exterior side, and a lower edge remote from the top wall, wherein the exterior side of the neck and the interior side of the skirt have cooperating rotational connection members, preferably first and second screw threads (16, 23) on said neck and skirt respectively, wherein the cap has two diametrically opposite wing parts, which are integrally moulded of plastic material and extend in a vertical plane outward from said skirt in a lateral direction over a wing part length, characterized in that each wing part has a base portion embodied as a wing panel and an adjoining top portion with two diverging top protrusions that extend upward from the base portion and diverge from one another defining a Y-shaped vertical cross-section of the wing part together with the base portion. wherein the cap comprises a top wall and a downward depending skirt, said skirt having an interior side, an exterior side, and a lower edge remote from the top wall, wherein the exterior side of the neck and the interior side of the skirt have cooperating rotational connection members, preferably first and second screw threads (16, 23) on said neck and skirt respectively, wherein the cap has two diametrically opposite wing parts, which are integrally moulded of plastic material and extend in a vertical plane outward from said skirt in a lateral direction over a wing part length, characterized in that each wing part has a base portion embodied as a wing panel and an adjoining top portion with two diverging top protrusions that extend upward from the base portion and diverge from one another defining a Y-shaped vertical cross-section of the wing part together with the base portion.