These are unused items but without the original packaging and they are currently setup for use with Kirby Morgan M-48 MOD-1 full face mask ( listed elsewhere ) .

From the manufacturers website:

The OTS EM-OTS2 Earphones and Microphone assembly has an improved design including : a new PTT circuit, an added kevlar strength member to increase Hi-Use Cable durability, improved earphone cable length and strength as well as sporting the new ME-150 microphone!

This OTS dual earphone and microphone assembly is designed to allow the user to connect either Hard-wire or Through-water communications to the Guardian Full Face Mask stocked by Northern Diver.

OTS offer a wide variety of earphones/microphone assemblies to fit many different styles of FFM including: Interspiro AGA, Kirby Morgan EXO26, Kirby Morgan M-48, Scubapro FFM and Draeger Panorama FFM. Please contact us to discuss buying assemblies for these types of masks. 

The configurations can be endless depending on the application. The following configurations are the most commonly used. Custom Earphone/Microphone (E/M) Assemblies can be manufactured upon request. However, off the shelf assemblies will be more readily available.

ME-150 Hot Mic® NEW, noise canceling, salt-water resistant, pressure-resistant studio quality microphone

Super Mic is a water proof, pressure tolerant ceramic microphone with a compact, lightweight design and noise cancelling properties reducing background noises for clearer communications
All standard E/M Assemblies include a Push-to-Talk (PTT) button used only for through-water communications; dual 150-ohm earphones, and earphone covers.