Lyman .58 caliber, 510 grain Minie bullet mold, single cavity, steel blocks only. Hollow base Minie bullets load easily, and expand to engage rifling. These precision mold blocks are made in the U.S.A. and tend to cost a bit more than other brands. They are nice quality. Special steel alloy mold blocks hold heat, for even casting temperature. Steel blocks almost never wear out, if properly stored. Blocks are made in one size, cut with two cavities for small bullets, or single cavity for large bullets. Mold handles are sold separately.