The Bose A-20 is the same NR technology 'leap' from the Bose X as the Bose QC-2 is to the Bose QC-15. Both the QC-15 and the Bose A-20 added an external mic on each ear cup that allows the NR 'anti-noise' to more accurately model and therefore cancel the noise that is likely being heard by the wearer, as well as new ear molds that are 'improved'.

I'm 99% sure the A-20 is TSO'd (Bose's selling point of buying an 'aviation headset' vs. the same technology in a 'non-aviation headset' @ 1/3 the price), but, once you find out the real meaning of what it takes to make a headset TSO'd (virtually nothing) and what it takes to maintain a headset's TSO certification (not much, but NOBODY does it), and how many pilots are not flying with TSO'd headsets (anyone with custom ear molds, for starters) what you might want to really be asking is not "is the headset TSO'd", but rather "will the FAA or my chief pilot think I'm using a TSO'd headset if I use the A-20"?