When it comes to reloading equipment, no one does it better than RCBS. So add to your first class equipment to help you achieve maximum accuracy with the RCBS 3-Die Roll Crimp Set. This 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.