Lyman's Deluxe Anodized Aluminum Loading Blocks are made for precision reloaders who want their equipment to be as high quality as the ammunition that they produce. The blocks are CNC milled from a solid billit of 6061-T6 aluminum to tight tolerances for a close fit to specific cartridges, unlike the common one-size-fits-all plastic blocks. The blocks are made in three sizes to fit most common rifle head sizes, and will hold 50 rounds. Blocks come with stick-on rubber non-slip feet to keep them from sliding on your bench. .388" hole size - fits: 17 Rem, 17 Rem Fireball, 204 Ruger, 222 Rem, 222 Rem Mag, 223 Rem, 300 AAC.