TRN BT20 Bluetooth V5.0 Ear Hook 0.78mm 2Pin Connector Earphone Bluetooth Adapter for UM3X W4R UM18 UE11 ES5 UE18 EN700 EN700PRO EM5 Earphones

This product is a great way to make 2 Pin UIEMs/CIEMs truly wireless. The main downside is limited Codec support, basically going to be SBC, I have not tried on a Apple device but I would assume they would work. Mind you that claims that BT5.0 makes music better is not necessarily true. Just because BT5.0 can send more data due to bandwidth enhancements over BT4.x, codec support is key to having great audio quality. What BT5.0 does do is keeps the headset from dropping out. In my testing I was able to walk into an adjacent room and still have the TRN BT20's stay connected to my Android device.Don't get me wrong the audio quality is not bad at all for say being on the bus/train or at the gym, but if you are an audiophile with an expensive set of UIEMs/CIEMs you will not be able to do the critical listening that you would get from a wired connection.I'm not an audiophile by any means and found little difference between a unbalanced cable and the TRN BT20. However I also know through experience, my "little difference" is usually countered by the audiophiles I do know with "there is a huge difference you can't hear that?"Charging is a little off putting but understandable. The TRN BT20's come with a USB-A to 2x micro USB(s), it's a split cable that allows both the batteries in the ear pieces to be charged at the same time. I say it is off putting mainly because if you lose the cable you won't be able to find another easily but it's not a show stopper as any micro USB cable will work to charge the ear pieces.Battery life is decent for this type of device, I haven't put them totally through their paces but on a set of CIEMs at 54 Ohms, 1/2 volume (50 out of 100) on my device; I'm getting about 3-5 hours. Which while not the 6 hours as described, it was expected to be short of the timeframe as all electronic descriptions will vary due to different use cases.Comfort wise the earhook is not adjustable but is not uncomfortable either. When receiving the TRN BT20's I had expected the weight or the earhook to be issues. In actuality, the TRN BT20's are almost no different then using a wired cable without the cable getting stuck on jacket zippers.Pairing was insanely easy as you just hold down the multi-function button (MFB), there is only one button per side, and then using the device they are connecting to finalize the connection. The downside to using a MFB is the directions are very limited. So I am still trying to figure out if there are other capabilities of the MFBs, like double presses, long presses, difference between long and short presses, etc. So far all I can definitely say is that using the MFB on either ear piece will cause the audio player to play/pause. I have not tried call quality for the microphone, i.e. me talking to someone. I assume that the audio should come through fairly clear on my end though.I recommend these for those that understand and/or need a truly wireless way to listen to their UIEMs/CIEMs; that the TRN BT20's are designed as a convenience for those with UIEMs/CIEMs but should not be used for critical listening.I would rate the TRN BT20's four stars if more audio codecs (APTX, APTX-HD, APTX-LL, LDAC, etc.) were supported. Hopefully in the next release that will be possible.

Have a pair of Massdrop+ hooked up to these. Honestly, not much difference between these and a wired connection except for a bit of hiss. There's a bit of a noise floor with these, but given the price I think it's reasonable. Controls work fine, pairing was easy.Given the alternatives for hooking your own IEMs to bluetooth, I sincerely think this is the best option. Not having a cable dangling down or around your neck is pretty liberating. They don't have the auto connect, charging case or other functions, but if you go into this with the correct expectations you won't be let down.

I got this to use with my KZX IEMs and they are working excellent. The sound quality is awesome! Works in SBC mode with my Hiby-based players and AAC with my phone. The battery lasts, although I listen at lower volumes.

Hard to pair, troublesome to charge, short battery life and looks and feels cheap.

The head set do not sync to each other automatically. You have to pair the units to together each time you turn on and they don'y always cooperate. If not paired you only get the right or left. It takes several attempts to get the sync to work. Instruction are vague.

Works well with my KZ iems, the aptx works well with Bluetooth 5.0, I use them with iOS, MacOS, and TVOS