Materion Brush Performance Alloys MoldMAX HH (High Hard) Alloy is the premier Beryllium Copper Flat Bar. This alloy has a hardness and strength comparable with standard tool steels but its thermal conductivity is at four to six times higher. MoldMAX HH Alloy is used for injection mold cores and cavities and blow mold pinch-offs. Its high hardness provides durability in applications where other high conductivity copper alloys fail. The alloy resists galling against other mold alloys, including itself.