The mic and speakers are pretty good. That's the biggest plus with these. However, that wasn't enough for me to keep them.
I returned this headset because it is extremely uncomfortable to wear. It's quite heavy, and it's so tight that it feels like a vice grip squeezing your head. I couldn't do more than 20 minutes without taking it off for a rest. And it kept sliding off as well. If you lean too far forward or backward, down it goes, notwithstanding how tight it is. And also, the earmuffs are COMPLETELY SUFFOCATING OF ALL OUTSIDE SOUND. You will hear next to zero outside noise when you put these on. The padding completely swallows your ears. I actually don't like the idea of that very much. I saw a news story one time about this kid that got his legs cut off by a train because his earbuds were totally effective at sealing off all outside sound and he didn't hear the train coming down the tracks. I personally like a modest amount of outside noise creeping in so I can be somewhat aware of what's going on around me. I felt a little too cut off from the world while wearing these, and I wasn't comfortable with that.
Buyer beware; this seller charges a restocking fee of about $15, so if you return them you will not get all of your money back.
This other Plantronics headset here (see link) is the one to get:
Plantronics 204446-01 Blackwire C325-M Headset
I'm much happier with this other one. It costs less, it's lighter and more comfortable, and I couldn't tell any difference in the mic or speaker quality.