Clockwork, I woldn't be caught without my buff in cold weather. One layer over my ears in sunny temps of 50-65 degrees. Doubled or worn as a balaclava for temps of 30-50. Below that I haven't a clue and I don't care to find out.

It is very thin and fits very well under a helmet. Tons of the pro teams are buying them and huge with the motorcycle crowd.

I discovered that worn one layer in warmer weather cuts down the wind roar in my ears without muffling my hearing.