A mold comprising a core plate receiving a core insert, a cavity plate receiving a cavity insert and an ejection mechanism configured to eject the core insert is disclosed. The core insert defines a first molding surface and the cavity insert defines a second molding surface cooperating with the first molding surface. The ejection mechanism comprises a top plate, a bottom plate, an ejection rod and a gasket. The ejection rod includes a first end in contact with the core insert in the core plate and an opposing second end fixed with the top plate, the bottom plate and the gasket by the fastener and the locating piece. The top plate drives the ejection rod to eject the core insert.