Abstract: A closure system for refillable containers includes a closure ring with a central opening and an annular skirt with a tab, a flange adjacent to the central opening and an annular recess between the flange and a wall of the closure ring; a sealing member having a central portion with a diameter larger than the central opening and an annular flange, the flange fitting within the annular recess, an upper portion fitting within the central opening; a container neck with external screw threads that engage the internal screw threads, a locking ring with a notch defined by at least one ramp adjacent to the notch, the notch configured to accept and hold the tab as the closure ring is screwed onto the container neck; the sealing member compressed between the closure ring and the container neck when the closure ring is screwed onto the container neck.