QC15 or QC25? I have both. The QC15 original uflymike (not Harmony) has been discontinued, however this is the only TSO'd version out there to my knowledge. The Harmony, which you can get for the 15 or 25, is not yet TSO'd, and I believe will only be TSO'd for the 25.

The tough part about the QC15 is Bose designed them so that when the AAA battery in it dies, not only does the noise canceling go away, but all sound goes away. That's why in order for the old uflymike (A100T) to be officially TSO'd you technically had to have TSO'd earbuds that plugged into the headphone jack on the model that you wore underneath the headphones. The advantage of the QC25 is much better noise canceling and the sound still works when the battery dies. I wore the non-TSO'd QC25 headset my entire time in the left seat at CPZ with numerous check airman and the FAA and no one ever complained. My idea was if anyone ever complained about it I'd just rock the David Clark headset for the trip. That never happened until I came to my new job and on my second IOE trip the captain asked me if that headset was TSO'd, to which I told him it wasn't so I wore the ship set. Now back to wearing the TSO'd 15's until they can get the TSO approval process completed for the 25's...

Hope that helps!