I gave 3 stars overall because some of the issues may be related to my equipment (*cough* Apple *cough*), so it may not be entirely Cowin's fault. For the exact purpose I bought these for - to drown out office noise when I return to work after pandemic shutdowns - it works well. I'm using it as an alternative to the wired headphones that I've used up until now, but which are not at all noise cancelling, and which bother others when I use them at any kind of volume that drowns out the background because they have an open back. At this price point for these noise-cancelling headphones, I'm satisfied (but nothing more than just satisfied) with just that use case. But are a couple of big gotchas:
Music quality with Bluetooth is good only when connected to my Android (Pixel 4a 5G). When connected by Bluetooth to my Macbook Pro (15-inch, 2017, running Big Sur 11.2.3 20D91) there is a high-pitched fluctuating noise constantly. The sound itself when connected by Bluetooth to my Macbook Pro is also occasionally "glitchy" - not sure how else to describe it. I don't get either of those artifacts when I use wired headphones with my MacBook Pro, so it's definitely in the Bluetooth connection (not my Spotify settings), and it's probably Apple's fault. There, I said it.
So, no problem, I'll listen to Spotify on my phone, where it sounds fine. But, when I placed a phone call (not Skype, Zoom, or any other conferencing service - an actual phone call), using the headphones as a Bluetooth headset, the caller said my audio was choppy. I had to disconnect the headphones to continue the call. I was hoping for better, but I already had to remove my wired headset whenever I wanted to use the phone, so nbd, I guess.
Bottom line, I don't have time to dig in on solving the problems I noted when my primary use case is satisfied. They don't work flawlessly with my equipment out of the box, and that's disappointing.
All of the above was with the phone sitting on the same desk where my computer is, and me sitting in front of the desk, so none of this is Bluetooth range related.