Abstract: The invention relates to a collapsible core for a mould. The core comprises three relatively movable assemblies. The first assembly carries a cone, the second assembly carries an inner set of segments which form part of the core surface and engage the cone and the third assembly carries outer segments moved by inclined pins on the second assembly. As the assemblies are moved together the outer segments move radially outwards and the inner segments move axially in between them. Then the inner segments move radially outwards and the cone fills the center of the core. On reversal of the movement, the core is collapsed to enable it to be withdrawn from the moulded article.