RCBS pioneered and developed 3-Die Sets for straight-wall rifle and pistol cases. The Carbide Sizer Die sizes the case and de-primes (the carbide sizer ring eliminates the need to lubricate). The Expander Die expands the case to the proper diameter to accept the bullet, and it imparts case mouth flare/bell for bullet feeding. The Seater Die seats the bullet and roll crimps. Standard 7/8"-14 Thread Carbide Ring Sizing Die Proprietary Die Steel Set Includes Sizing Die, Expander Die, Bullet Seating Die All RCBS dies are machined to exacting tolerances, hardened and finished to the highest standards in the industry Component and Caliber Reference Table