Flat modular type cord.
Commonly called an RJ9, RJ10, or RJ22 cord.
4P4C modular handset style plugs on each end (like a coiled handset cord, not for wall to phone).
Silver colored jacket.
26AWG, 4 conductor.
Used for special application phone equipment, headset amplifiers, inverter remotes, etc..
Can be used as a replacement "amplifier to handset jack" cord on Plantronics and other similar systems.
Also used for a microphone extension cord on compatible systems with RJ9/RJ22 type jacks. Also used for tanning bed timers and inverter remote controls that use RJ9/RJ22 type jacks.
Each one is professionally made and tested for quality assurance before it is shipped.