The Gold Medal Match Series comprises the finest reloading dies built by RCBS. The Full-Length Sizer Die features a self-centering changeable neck bushing that lets reloaders precisely set the amount of case neck tension on the bullet. This reduces work hardening of the case neck brass, prolonging case life and increasing accuracy. However, getting these benefits requires the use of high-end brass with consistent neck thicknesses. By removing the neck bushing, the Full Length sizing die can also be used as a bump die to set headspace back the desired amount. Neck bushings (sold separately) are REQUIRED and are available in .001-inch increments from .189-inch to .365-inch. Note: Neck Bushings are not included.