FEATURES-Caliber: .357 Sig-This two-die set is intended for reloading bottleneck cases, & consists of a Full-Length Sizer Diewith an Expander-Decapping Unit, & a Seater Die with Bullet Seater Plug.-The Full-Length Sizer Die brings the case to SAAMI minimum cartridge dimensions-It sizes the outside of the case, de-primes & expands the neck to accept the bullet-The die vents to prevent case damage caused by trapped air & for excessive lubricant-Headspace is held to minimum tolerances to avoid changing the case body length during full length sizing-Then included Seater Die has a built-in roll crimper to secure the bullet at the same time as it's seated