All SAECO moulds are machined from solid cast iron blocks one cavity at a time. Using the same cutting tool (cherrie) for each cavity duplicates the previous one. You don't need to pay a premium for matched cavities. SAECO even developed its own blend of coppyer alloyed pearlitic cast iron for tight grain structure, dimensional stability and extended life. The steel sprue plates are held firm against the mould blocks by high-temperature spring washers to insure uniform bullets with square bases.