This collet is required for a reloader using the Forster Original or Power Case trimmer.Notes: For cartridges not listed, use the case's base size to determine the correct collet. For example, for a 35 Whelen, it has a 30-06 Springfield base case size. Most reloading manuals will list the original case for Wildcat and other odd cartridgesSPECIAL NOTE: This collet will not work with Classic Case Trimmer