Abstract: The invention provides a removable closure system comprising a tubular member having an internal surface with an internal profile therein, an entrance end and a plug end, the internal profile providing a dog shoulder and a plug stopping shoulder. A plug assembly is positioned within the tubular member. The plug assembly has a plug suitable for insertion through the tubular member at the entrance end and past the dog shoulder, a plurality of dogs. The dogs are moveable between a collapsed and an expanded condition, the collapsed condition suitable for insertion of the plug assembly through the tubular member past the dog shoulder and the expanded condition suitable for engaging the dog shoulder. When the plug assembly is placed in the tubular member against the plug stopping shoulder, and the dogs are in the expanded condition engaging the dog shoulder, the plug assembly is removably secured in the tubular member.