Crimp dies are supplied in pairs and have a 1.6mm pin crimping cavity (except size X, which is 1.75, and ZPLUS, which is 1.8).
Required to assemble rearTwist and Push-Pull BNC connectors, the die set has one or more larger cavities for crimping the connector ferrules and may be suitable for more than one connector size.
The letters at the end of the description indicate the cavities' sizes.