RCBS bullet molds are meticulously machine one at a time from iron blocks. High grade machine tool grade steel is used exclusively in machining molds to maintain precision tolerances. After machining, molds are heat blued. Hardened steel pins provide alignment of the block halves throughout the casting sessions. The sprue cutters are made of tough steel plate and are held flat and secure by an adjustable pressure washer. Mold handles sold separately.