Rare that I leave product reviews but making an exception for these earphones.
I've been a reluctant adopter of Bluetooth earphones after iffy experiences in the past. In general, I've always run into audio drop-outs while outside and using wireless headsets. It didn't seem to matter whether I was using audiophile equipment or cheapy stuff, the result was always the same: drop-outs.
So it was with some trepidation that I bought these earphones after my corded Sennheiser running earphones died. I'd already mentally accepted the likelihood of me returning them, but figured they were worth a shot.
Having just completed an evening outdoor run using them, I can report that I didn't suffer a single drop-out, the audio was clear and loud and the fit was comfortable and secure. The flexible round-the-head design meant wearing a woolly hat in these sub-zero temperatures wasn't awkward, which was always a problem with the Sennheisers.
Sure, they won't win awards for their audio dynamics, but that's not why I bought them. In the context of a gym or an outdoor activity where you're looking for the company of an audiobook or the motivation of a song, they're ideal.
As a reference point with regard to the Bluetooth connection stability, my phone is a OnePlus 5T and it's secured at waist height when running. I'm 6'2.