The RCBS Full Length Die Set is a must for any serious reloader. The Full length sizing die sets the cases to SAAMI minimum cartridge dimensions decapping the shell and expends the neck to accept the bullet in one action. The die is vented to prevent trapped air or excessive lubricant from causing damage to the shell casing. Seater die has a built in roll crimp to secure the bullet while seating and avoid case damage due to varying cartridge lengths. Shell holder sold separately.