The Lee Precision Factory Crimp Die is designed to give reloaders the perfect crimp on each round of reloaded ammunition. The Factory Crimp Die crimps the bullet more firmly in place than any other die with more uniform pressure. The Factory Crimp Die features a collet that squeezes the case mouth into the crimping groove for a firm hold. It is nearly impossible to buckle the case when crimping when compared to a regular roll crimp die. Lee's testing has shown that using a Factory Crimp Die provides a more uniform pressure curve, increasing the accuracy of any bullet. Shellholder sold separately.