A closure for a container, the closure comprising: a base having a first portion and an underlying second portion fixedly attached thereto, a passageway extending through the first and second portions in a direction generally parallel to a longitudinal axis A of the base, a cap movably attached to the base, the cap being movable between a first position in which at least a portion of the cap blocks at least a portion of the passageway and a second position in which the cap is spaced-apart from at least a portion of the passageway to allow contents from within the container to pass therethrough; at least one first fastening member is positioned on or in the first portion of the base and at least one complementary second fastening member positioned on or in the cap, wherein the second fastening member engages the first fastening member to align the cap with the base; a first width W p of the passageway in the first portion, proximate a first end of the base, is smaller than a second width W P2 of the passageway in the second portion, proximate a second end of the base, as measured generally perpendicularly to the longitudinal axis A, wherein at least a portion of the second portion of the base is configured to be attached to at least a portion of an opening of a container such that the passageway is in registry with at least a portion of the opening, characterised in that the second portion of the base has a reduced cross-sectional area as compared to the first portion, and the cap generally surrounds the entire first portion of the base when the cap is in the first position, the closure comprising a seal on one of the cap and the base, at least a portion of the seal being positioned and at least partially compressed between the cap and the base when the cap is in the first position to seal the passageway. a base having a first portion and an underlying second portion fixedly attached thereto, a passageway extending through the first and second portions in a direction generally parallel to a longitudinal axis A of the base, a cap movably attached to the base, the cap being movable between a first position in which at least a portion of the cap blocks at least a portion of the passageway and a second position in which the cap is spaced-apart from at least a portion of the passageway to allow contents from within the container to pass therethrough; at least one first fastening member is positioned on or in the first portion of the base and at least one complementary second fastening member positioned on or in the cap, wherein the second fastening member engages the first fastening member to align the cap with the base; a first width W p of the passageway in the first portion, proximate a first end of the base, is smaller than a second width W P2 of the passageway in the second portion, proximate a second end of the base, as measured generally perpendicularly to the longitudinal axis A, wherein at least a portion of the second portion of the base is configured to be attached to at least a portion of an opening of a container such that the passageway is in registry with at least a portion of the opening, characterised in that the second portion of the base has a reduced cross-sectional area as compared to the first portion, and the cap generally surrounds the entire first portion of the base when the cap is in the first position, the closure comprising a seal on one of the cap and the base, at least a portion of the seal being positioned and at least partially compressed between the cap and the base when the cap is in the first position to seal the passageway.