There are two families of “D” shaped connectors, the first of which is the
D-SUBMINIATURE type. Each of these connectors is generally identified by the number of contact pins with which it is equipped.  Popular standard sizes are 9, 15, 25, 37, and 50 pin units, and there is an MK series punch designed for each of these.

The entire line of punches are designed to make a hole of sufficient size to accept the larger of either plug or receptacle, be it metal or plastic

Documentation

The other style of connector with a “D” shaped shell is known as a RIBBON connector. These units have a bus type contact configuration, as opposed to the pin and socket type arrangement. Ribbon connectors are also generally identified by their number of contacts. The popular standards are the 14, 24, 36, and 50 contact models, and an RB series punch is available for each of these.

Also available is the MK-50-3M, a special punch used for mounting the 3M Delta Ribbon Connector.