Sinlge lense = MX use. Double Lense = Snow use.
With a single lense it will constantly fog because of the tempature of your face is way warmer than the outside air temp causing fogging. I scratched the inside lense of some A-frames and tried taking the lense out and using them but what I said will happen quickly.
Your a idiot get a snow lense not a mx lense.
Have A Big M
Then Go Have A Cry
To get back on topic instead of name calling for no reason...
I wouldn't buy the single lens if you can help it. It works fine if you are always moving and just doing general groomers and laps, etc. But, if you hike at all, whether park or pow, it will fog on you, as someone above mentioned.