The case holder holds the case for trimming. Cases are held by body taper, NOT case head. Diameter of case and case length determines case holder size. The FIRED Case Holders are for Neck Sized Cases. The case holder holds the case for trimming. Cases are held by body taper, NOT case head. Diameter of case and case length determines case holder size. If they DO NOT make a "New Case" holder for your caliber this will be all you need, and refer to these as Standard Fired Holders For example: Wilson only makes ONE holder for the 222/223 Remington. This will work for all Fired / New and Full Length Resized Brass Made in the U.S.A.