Lee crafts its mold blocks from high-quality aluminum, ensuring superior rust resistance compared to traditional iron or steel. Aluminum molds offer quicker heating and cooling times, allowing bullet casters to produce high-quality bullets after just a few casts. Additionally, aluminum blocks weigh one-third as much as their iron or steel counterparts, significantly reducing fatigue during extended casting sessions. For exceptional accuracy and consistency, each mold block half is CNC-machined, ensuring perfect roundness and precise size control. The listed weights reflect Lee's suggested alloy, but actual weight may vary depending on the specific alloy mixture used.