With the X Die Full-Length Die Set, you can trim your bottleneck cases once and never worry about trimming again. This set includes the X Die Sizer and Standard Seater Die, featuring a specially designed mandrel with an expander ball and decapping pin. Its patented design eliminates the need for repetitive trimming after an initial .020 inches trim to standardize the case length. The X Die doesn't shorten the case rather, the mandrel reduces case growth by preventing the mouth from contacting the mandrel during sizing. Thanks to the precise tolerance between the mandrel and die neck wall, the neck wall of the case stays consistent and doesn't thicken as the length is resized. After initial sizing, cases may grow slightly, but they will quickly stabilize below the maximum case length, ensuring no loss of accuracy or case life. For reloaders who already own a set of regular dies for their chosen caliber, simply order the X Die full-length Sizer for a hassle-free experience.