Full length die sets are for bottleneck rifle and pistol cases, and they include a full length sizing die and a seater die. The RCBS Full Length Die Set for .338 Lapus Mag will bump the shoulder of the case to extend the die and is adjusted up or down in the press. Use a cartridge headspace gage tool to get the correct shoulder bump. The full length die also sizes the body of the case so it will chamber easily for the next firing, then the die decaps the spent primer. The expander ball passes through the neck of the case and sizes the neck to the correct tension. Cases must be lubricated before full length sizing. The die set will seat bullets correctly in full length sized cases or neck sized cases. Has a built in crimp ring enabling you to crimp the case into the bullet. Easily adjusted to crimp or not to crimp by raising or lowering the position in the press.