The 3-Die Roll Crimp Set is for loading straight-wall cartridges. Its steel Sizer Die sizes the case and de-primes. Note: Cases must be lubricated. 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. Features a hardened steel Sizer Die (case lubrication required) Expander Die to properly expand case to accept bullets Roll Crimp Seat Die to crimp case to bullet to eliminate bullet movement Comes in green storage box All RCBS dies are machined to exacting tolerances, hardened and finished to the highest standards in the industry Made in USA