The L.E. Wilson Decapping Base is the perfect companion for the L.E. Wilson Decapping Punch. The base will collect the spent primers as they are removed from the case. Decapping punch (required) is sold separately. Notes: Base is for use with Wilson Decapping Punches - sold separately Base and Decapping punch are used to remove primers from military casesTo Determine the Correct Size, Simply Measure your Case Head Diameter. For example a 223 Remington head measures .375" so you would need a .380 Base