A slider valve assembly for connection to a spout of a flexible container, the assembly comprising: a cap member having a central opening and being adapted to be secured to the spout of the container; a valve member defining one or more side openings in communication with a central bore, said valve member being slidable within the central opening of the cap member and lockable into a closed or open position; wherein the assembly comprises: an outlet member for engaging to and actuating the valve member, said outlet member defining a hollow interior portion in communication with the central bore of the valve member and having a handle portion for moving the valve member into its open or closed position by depressing or pulling the handle portion, wherein axial movement of the outlet member relative to the cap member causes sliding of the valve member into a closed or open position; in the open position the one or more side openings of the valve member being in communication with the container, thus permitting the contents of the container to be dispensed through the outlet member, characterised in that axial movement of the outlet member relative to the cap member can lock the valve member into a closed or open position, and in that the outlet member can detachably engage to the valve member. a cap member having a central opening and being adapted to be secured to the spout of the container; a valve member defining one or more side openings in communication with a central bore, said valve member being slidable within the central opening of the cap member and lockable into a closed or open position; wherein the assembly comprises: an outlet member for engaging to and actuating the valve member, said outlet member defining a hollow interior portion in communication with the central bore of the valve member and having a handle portion for moving the valve member into its open or closed position by depressing or pulling the handle portion, wherein axial movement of the outlet member relative to the cap member causes sliding of the valve member into a closed or open position; in the open position the one or more side openings of the valve member being in communication with the container, thus permitting the contents of the container to be dispensed through the outlet member, characterised in that axial movement of the outlet member relative to the cap member can lock the valve member into a closed or open position, and in that the outlet member can detachably engage to the valve member. an outlet member for engaging to and actuating the valve member, said outlet member defining a hollow interior portion in communication with the central bore of the valve member and having a handle portion for moving the valve member into its open or closed position by depressing or pulling the handle portion, wherein axial movement of the outlet member relative to the cap member causes sliding of the valve member into a closed or open position; in the open position the one or more side openings of the valve member being in communication with the container, thus permitting the contents of the container to be dispensed through the outlet member, characterised in that axial movement of the outlet member relative to the cap member can lock the valve member into a closed or open position, and in that the outlet member can detachably engage to the valve member.