The Redding Decapping Die is used to deprime your cases prior to sizing. This allows the cases to be cleaned before sizing so as not to scratch your sizing dies. The small decapping die can be used for 22 through 50 caliber cases with lengths up to 2.625". For longer case lengths up to 3" use the large decapping die. The large decapping die can be used for 25 through 50 caliber cases.