A Clear Tune Monitors (CTM) Wireless Cable is a much better option than this. For $10 more, you get Bluetooth 5.0 & 10 hrs. of battery life. You also get a much better remote control.
LaserGuidedSockI did a short review here:
https://www.massdrop.com/talk/21155/product-report-ctm-wireless-cable-w-mic
I don't know what protocols are used but I've asked them the question & I'm waiting on a response. All I can say is that my cable has been performing flawlessly. There are some minor quibbles that I mention in the review but nothing that detracts from its performance.
MaverickAHThanks. Now this definitely just made my choice much harder. I'm thinking about maybe getting both and returning the one I like less. Or maybe even getting a 2nd pair of IEMs just to fit them.