The Ideal 30-581 Combo Die Set if for use with the Crimpmaster Crimp Tool to crimp RG58, RG59/62 and TNC/BNC connectors. It provides a consistent crimp with each use. Die changes are made quickly and easily with a screwdriver. The hex hole sizes are .255" (6.48mm), .213" (5.41mm), and .068 in. (1.73mm).