The RCBS 28304 represents a 3-Die Roll Crimp Set that\'s perfect for working with straight-wall cartridges. It includes a steel Sizer Die, which is responsible for sizing the case as well as de-priming. It\'s important to remember that cases need to be lubricated.Additionally, this set also contains an Expander Die. Its function is to widen the case to a diameter suitable for the bullet. It also adds a flare or bell to the case mouth, facilitating bullet feeding.Last but not least, the set is equipped with a Seater Die. Its job is to accurately place the bullet and apply a roll crimp. All these elements combine to create an efficient and smooth reloading process.