Lxx's original priming shell holders were designed to maximize compatibility and fit more cartridges in to each shell holder therefore Lee's original shell holders are a bit sloppy. Our Priming Shell Holders are designed for competition reloaders. They have tighter tolerance than Lxx's original ones. They are designed for specific cartridges and their families. Our Shell holders are made of 420 Stainless Steel, CNC turned and milled. They were hardened to 45-50HRC . Please note before you purchase: These are NOT reloading shell holders, they are flat type and will ONLY SEAT PRIMERS. NOT FOR SIZING OR BULLET SEATING! Available in the following sizes: 223REM and its families share the same rim and base eg 204Ruger, 222,5.56,300ACC; 308WIN and its families share the same rim and base eg 243, Creedmoors, 260Rem,270,6Br; 7.62*39 and its families share the same rim and base eg Grendels, PPC; 300 Win Mag and its families share the same rim and base eg 7RM,SAUM, PRC,300WSM; 338 Lapua Magnum.