Case Holders allow you to trim cases in your Wilson Case Trimmer. The Q-Type case holders hold the case with an easy to use cross pin. Use this type whenever possible because the regular pistol case holders require you to tap the pistol case in, which is more difficult than the rifle cases because of the lack of a body taper. Some Calibers May Not be Compatible with Shark Fin or Case Holder Clamp For Use with the Wilson Case Trimmer Designed to be Used with Straight Walled Rimmed Pistol Cases Made in the U.S.A.