The Area 419 ZERO M-Series Sizing Dies are a great product with some incredible features - but they require a wide-rimmed shellholder. These have long been available for purchase with the dies, and are now available on their own. Cartridge Fits:223 is meant for .384a ^2 bolt face cartridges, including 223 Rem, 300 Blackout, etc.308 is meant for .473a ^2 bolt face cartridges, including 308, 6mm/6.5mm Creedmoor, GT, Dasher, BR, etc.Magnum is meant for .540a ^2 bolt face cartridges, including 6.5 PRC, 7 Rem Mag, 300 Win Mag, etc. This will NOT fit larger .585a ^2 bolt face cartridges like 338 Lapua.