Redding has solved the problem that has plagued ordinary carbide dies since their invention. The little ring in a standard carbide die had to do double duty. It sized the top of the case to properly hold the bullet but then continued to size the whole body of the case as well. Unfortunately, these two areas need to be sized at different diameters, so carbide dies of the past have always been a compromise.
Redding's solution to this problem is a unique design, incorporating two carbide rings within one sizing die. The upper ring is positioned to size only the bullet retention portion of the case while the other is located to properly size the case body without overworking the brass. Sized cases will not only look and function better but brass life will increase.