RCBS Single Stage shell holders are built from hardened steel and designed to properly align the case with the reloading die in single-stage and turret presses. They’re sized to fit specific case heads and capture 0.125 inch of the case head for proper SAAMI headspacing. 223 Remington (5.56mm) 204 Ruger 17 Remington 17 Remington Fireball 221 Remington Fireball 222 Remington 222 Remington Magnum 6mm x 45 7mm Thompson/Center Ugalde 300 AAC Blackout 380 Auto Pistol 9mm x 18 Ultra RCBS shell holders are built for Single Stage and Turrets Presses. RCBS shell holders are manufactured to exacting tolerances. RCBS shell holders are hardened for years of use. RCBS shell holders ensure proper alignment between the cartridge and die. The Shell holders are cut to .125" depth for proper headspacing. RCBS Limited Lifetime Warranty.