This two-die set is for bottleneck type cases used in tight-chambering semi-automatic pump or lever-action rifles. It consists of a Small Base Sizer with an Expander-Decapping Unit and Regular Seater Die with Seater Plug. The sizer resizes cases below SAAMI minimums reducing the shoulder and body by a few thousandths. It also de-primes the case. The included Seater Die has a built-in roll crimper to secure the bullet at the same time it�s seated. To seat bullets without crimping simply unscrew the die until the crimp ring no longer engages the case mouth.