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. This model is compatible with the following calibers: 26/27/28/33/30 Nosler; 6.5mm PRC; 6.5mm RSAUM; 7mm/300 RSAUM; 300/338/375 RUM; 455 Webley.