Closure system and kit

A closure system for closing an opening of a container, comprising:

• a stopper member made of an elastic material and having a plug portion configured to fit into the opening of the container and a cover portion configured to abut a boundary surface adjacent to the opening of the container;
• a cage member configured to be mounted to the container;
• a cover member reversibly mountable to the cage member;
• and
• an integrity visualization member,
• wherein the closure system is configured to be in an assembled state in which the plug portion of the stopper member is fitted into the opening of the container and the cage member is mounted to the container,
• wherein the cage member is configured to apply a force to the cover portion of the stopper member to push the cover portion of the stopper member onto the boundary surface of the opening of the container when the closure system is in the assembled state,
• wherein the cage member has an aperture to access the cover portion of the stopper member when the closure system is in the assembled state,
• wherein the cover member covers the aperture of the cage member when being mounted to the cage member,
• wherein the integrity visualization member is configured to indicate an integrity of the closure system and configured to be positioned between the cover member and the cage member when the closure system is in the assembled state,
• wherein the closure system is configured such that integrity indicated by the integrity visualization member is recognizable,
• wherein the integrity visualization member is configured, in the assembled state of the closure system, to change in shape when the cover member is demounted from the cage member, and,
• wherein the integrity visualization member comprises a rupture structure configured to at least partially tear when the cover member is demounted from the cage member.