RCBS AR Series 308 WIN Die Set - Small base sizing dies size brass to minimum specifications and help to ensure that cartridges will chamber every time. The taper crimp seating die is helpful as it is a bit more forgiving die for crimping cases that have variable case lengths which help reduce bulges and buckled shoulders when crimping. Small Base Full Length Sizing Die, Taper Crimp Seating DieComes packaged in a plastic storage boxDies can be used in any reloading press with standard 7/8" - threaded dies