The MX505 fits great and is quite stable when I move. Sounds great too, at least most of the time. I especially like the boom mic - that's the key reason I bought it. In terms of sound quality, it's very clear, but I have had an intermittent volume issue where I would sound very quiet to people, and I could make the problem disappear by simply touching the headset gently or moving it slightly. The folks at Headsets.com have diagnosed this as likely a loose wire and sent me a replacement so we'll see what happens - I'm not sure if this is a durability issue with these units overall, or if I just got a lemon.
So the headset is great when it's working and I would definitely buy it again if the replacement unit solves the volume issue. The service from 1-800 Headsets is fantastic. I own my own business and know all about the value of good customer service - these folks are outstanding. If you're looking for a headset, you need to talk to them.
Rob Fisher
BC