Start priming in seconds, nothing to adjust. Includes small and large priming assemblies, no tiny parts to fumble with or lose. Effortless priming in the tightest pockets. Uses any brand press shell holder. Safe with all brands of primers. Works in any Lee Breech Lock press or 1 1/4-12 Breech Lock Update Kit | 1 1/2-12 Breech Lock Update Kit adapter. Mfg: Lee Precision