A mould system for moulding a receptacle is described. The mould system comprises a mould comprising a mould cavity and an opening, and a mandrel system comprising a reference point, a mandrel and an expandable member. The mandrel is at least partially located, or at least partially locatable, inside the expandable member and comprises one or more holes through which a fluid is flowable in use from an interior of the mandrel to an exterior of the mandrel to expand the expandable member. When the mandrel is at least partially located inside the expandable member, the mandrel system is positionable relative to the mould such that the reference point is at a fixed position relative to the mould and the mandrel, and the expandable member extend into the mould cavity through the opening such that there is a clearance between the expandable member and a base of the mould cavity opposite the opening. The expandable member and at least a part of the mandrel are moveable relative to the reference point to vary the clearance.