Capsule and plug for a concentrated refill capsule

A plug for use in a cap assembly of a refill capsule, the plug comprising:

• a hollow tubular body with an open proximal end and an open distal end, wherein the open proximal end is surrounded by a first rim that provides a proximal abutment surface for bearing against a frangible sealing component of a cap assembly;
• wherein the proximal abutment surface lies in a plane that is orthogonal to a longitudinal axis of the tubular body, and surface surrounds, in total, at least half of the open proximal end;
• a skirt extending around the tubular body, and comprising a tubular skirt wall arranged coaxially with respect to the tubular body, the skirt wall being spaced apart from the tubular body in a radial direction to form a plug recess between the skirt wall and the tubular body,
• wherein the skirt wall extends from a skirt distal end at which the skirt wall is connected to the tubular body, to a free proximal end,
• wherein the free proximal end of the skirt comprises:
• an outwardly extending flange comprising a distal facing abutment surface for abutting a rim of a refillable vessel.