Summary: The 2.5mm-USB adapter is the silver lining. I had an old 2.5mm Jabra hook collecting dust and somehow remembered it when the new headset's mic died. While the adapter might not have been the intent of the purchase, what I ended up with works great.
Pros: My trusty Creative Fatal1ty's mic gave out after two years of abuse. Since its speakers still work for media, I figured I'd go for a lighter single-ear headset. I've got a deep respect for Plantronics after my call center years, so a little hunting brought me to this little gem. Decent audio qual...
Cons: Note the past tense in that last line. Mic suddenly dropped to near inaudible levels within four hours of unpacking. Checked on two other computers and fiddled with the output switches to be sure, it's pretty much dead.
Summary: The plantronics was for my husband who claimed the bluetooth headset he had was knocking him off the call...so we got this headset. The audio is ok...but while driving it is hard to hear him. The noise in the cab in his new truck over powers his voice...so voice quality is somewhat ok.