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 so it will not move during recoil.