The QC15/UflyMike is actually available in a TSO'd version. However one needs to wear additional earbuds which is kinda redundant. No problems on the 737 as an FO with the mike on left side although it worked a tiny bit better on my Sennheiser HMEC 26. I used the Telex 850 but its reduction is actually not good enough, after 5 years of wearing it on the 737 i had a measurable hearing loss and switched to better products. Interestingly enough the company i work for tested several headsets and the 850 wouldn't be allowed under current health safety regulations, on the airbus fleet it would work out though as their flightdeck isn't as noisy.