Dual Ring Carbide Sizing Dies are the correct answer to the compromise that has plagued traditional carbide dies of all manufacturers since their creation. The traditional sizing ring is required to perform double duty which it can not do. It is required to size the case sufficiently to secure the bullet (with even the thinnest brass) which all do with some success. From that point however, all traditional carbide dies resize the remainder of your cases excessively. The price of this compromise is shortened case life of your overworked brass, unsightly appearance and less than ideal chamber fit which may lead to an adverse effect on accuracy.
The Redding solution is unique, incorporating two carbide rings within one sizing die. The upper ring is positioned to size only the bullet retention portion of the cartridge case while the other is configured to properly size the case body without overworking the brass. Your sized cases will not only look good and function better but brass life will increase.