Mogami W3159 features a very thin outer diameter 24 AWG twisted pair insulated with a foamed CPP (Cellular Polypropylene) dielectric, a served shield (spiraled, not braided) with a drain wire, and a thin outer jacket. It's very lightweight and flexible, but it needs to be treated kindly due to the thin jacket that is prone to nicks and scratches. Perhaps thin silk tubing as protective sleeving would be nice to use for a headphone cable project.
Don't let the low-price turn you off, since the audio performance is excellent due to the low dielectric constant of the cellular polypropylene insulation. It's an impressive cable for line-level use, AES/EBU applications, and DC umbilical builds. I plan to build some headphone cables with the Mogami W3159 when I get around to it, as I've had too much on my plate building other cables and power cords lately.
The Oyaide CIEM connectors seem to be a fine choice for the purpose and rather affordable when it comes to audiophile connectors. Sensible and attractive, I reckon.
The 4.4mm connector is very impressive, and appears to be the same design as a more expensive Stout product I've come across on the web. Having a set-screw type strain relief is ideal for a dual cable termination, and the thick walled barrel with carbon fiber layer is impressive. The outer diameter of the Mogami W3159 cable is thin enough to fit through a headphone cable splitter, such as an aluminum with carbon fiber design to match the 4.4mm plug.
https://www.redco.com/Mogami-W3159.html
https://www.ebay.com/itm/Oyaide-CIEM-connector-0-78mm-Gold-plated-plug-made-Japan-/133366388060
https://www.aliexpress.com/item/4000134369577.html
