Lee manufactures their mold blocks from aluminum, offering rust resistance and enhancing durability. Aluminum molds heat up and cool down faster than iron or steel molds, allowing for high-quality bullets to be produced quickly, often after only a few casts. Additionally, aluminum blocks are one-third the weight of iron or steel molds, minimizing fatigue during long casting sessions. To guarantee superior performance, each mold block half is CNC-machined to achieve unmatched roundness and size control. The weights listed are based on Lee's recommended alloy; however, actual weight may vary depending on the specific alloy mixture used.