The Kokoon NightBuds are, like the Amazfit ZenBuds or Bose Sleepbuds II, designed to be worn in bed so as to help the user fall asleep. To this end, they measure just 5.4 millimeters in depth, although they are not TWS. They have launched via Kickstarter, where they have amassed nearly 15 times their goal.
https://www.notebookcheck.net/Kokoon-s-ultra-slim-NightBuds-sleep-audio-earbuds-hit-the-US380-000-mark-on-Kickstarter.498308.0.html
"391% slimmer", impressive reality distortion field. I'll boycott them just for this despicable marketing.