The patented X-Die eliminates the need for repeated trimming after an initial case trim of .020" off the maximum case length. A specially designed mandrel contacts the case mouth and reduces the growth rate. Because of an extremely close tolerance between the mandrel and die neck wall, the neck wall of the case does not thicken as the case length is pushed back. Cases repeatedly sized in the X-Die will initially grow a few thousandths of an inch, then stabilize below the maximum case length with no discernable loss of accuracy or case life. Set contains X-Die Full Length Sizer Die and Seater Die. Shellholder sold separately. Notes: The RCBS X-Die eliminates the need for repeated trimming after an initial trim of .020" off the maximum case length to standardize the case.It does not shorten the length of the case. A specialized mandrel reduces the growth rate as the case grows as a result of the case mouth contacting the mandrel during sizing.Shellholder NOT included.