The NL4MP-ST is 4 pole chassis connector, black D-size flange, countersunk thru holes, screw termination. This chassis connector is not airtight.The speakON panel mount connectors are the standard chassis connectors for loudspeaker / amplifier interconnections. They feature a unique metal locking system, making contact only once fully locked. The speakON receptacles are robust, versatile and easy to terminate.