The addition of a smooth radius to the mouth of each shell holder around the shell plate ensures smooth functioning-especially when the shell plate is used with the Lock N Load Case Feeder(sold separately). In addition, the bevel on the retainer spring groove helps keep the spring in place when inserting cases into the shell plate. These shell plates will also work with the older model Hornady Pro-Jector press. This shell plate works with; 45 Colt, 454 Casull.