Abstract: A movable insert for a die-casting mold. The movable insert has a parallel-sided cavity which slidably receives a retractable core. The retractable core is movable between a retracted position within the movable insert to an extended position extending from the movable insert. The retractable core has a connector for its releasable securement to a locator which moves it between the extended and retracted positions. The retractable core is further provided with a sealing member extending thereabout and between it and the sides of the cavity walls. The sealing member provides a slidable seal between the retractable core and the sides of the cavity.