I got these to replace an old pair of Oakley Flak 2.0. I use the Oakley Plazma for XC MTB & downhill MTB. What I like most is that I can use them instead of goggles at the bike park for downhill. They breath better than goggles but still do a really good job keeping out dust. And for some reason, my sweat rarely gets on the lenses. They fit perfectly in a full face helmet too. Have never had an issue using them for XC either. Iï¿½ve used Oakley sunglasses for a long time & these are by far the best pair I've had for cycling, especially downhill with a full face helmet.