I just purchased a BO 105 with low impedance requirements for the headsets (military type) but planning on putting in new coms (high impedance). I purchased a very expensive ($1,200) low impedance noise reduction headset that worked “just ok” knowing that I will have to abandon them when I put in new coms. I decided to try the.H10-66 (much less expensive – under $600 – and non-noise reduction. They actually work better than the noise reduction ones (not sure why) and they have a switch that will switch them to high impedance once I get the new coms in. The set I bought worked great so I have now bought four more sets for the copilot and passengers.