Oil well perforators

An oil and gas well shaped charge perforator is provided comprising a housing, a high explosive, and a liner with a further insert liner where the high explosive is positioned between the liner and the housing. In use the high explosive will collapse the liner and insert causing two cutting jets to form. The insert may substantially cover the surface area of the liner or it may over only partially cover the liner, such as the apical portion of the liner or the base portion of liner. Alternatively the insert may be varied in thickness across the surface area of the liner. Typically the thickness of the liner may be between 1 and 10% of the liner diameter and the thickness of the insert may be between 1 and 200% of the thickness of the liner. The insert may be produced during the manufacture of the liner, but preferably the liner will be a retro fitted item.