Abstract: A hollow tubular outlet member and a cap fitting over the outlet member and rotatable relative thereto, the outlet member and cap having complementary conical end portions, an aperture in each conical end portion which can be aligned to define an opening which can be closed by rotation of the cap and wherein the cap and outlet have a co-axial tubular portion, one of such tubular portions being provided with at least one formation directed towards the other tubular portion and co-operating with a cam surface on the other tubular portion, the cam surface being shaped such that the conical end portions are urged axially into tighter engagement with each other during rotation of the cap to close the opening.