Neutrik has three lines of Ethercon type connectors:
A) "Ethercon Cable Connector Carrier", e.g. NE8MC. This is an XLR-style housing for pre-terminated Cat. patch cables with RJ45 plug. Outer diameter is 19mm (0.748").
B) "Ethercon Cat. 6 Cable Connector", e.g. NE8MC6-MO. This is a complete XLR-style connector. Outer diameter is 23.28mm (0.917").
C) "Ethercon Cat. 6A ISO (ISO = subscripted "A"), e.g. NE8MX6. This is a complete XLR-style connector. Outer diameter is 19.05mm (0.750").
A) are the original Ethercon series. We shy away from them because we had to many troubles with ready-made patch cables that do not fit.
B) is the (mechanically) best Ethercon in my opinion. The push-pull mating design not only provides a secure locking system but also prevents wiggle of the connector in the receptacle.
C) is the newest version and theoretically the most desirable because it meets Cat. 6A ISO standards. However it is not as stable in the receptacle
as version B).
Versions A) and C) are claimed to be mechanically compatible (I have not tested on my own).
Our latest systems use version C.