Wore the balaclava on a bike ride, when it was only 40 F outside and with a cold breeze. Given how thin and light the material is, I figured that it would help a bit, but that my ears would still get very cold, especially on the downhills where we would be approaching 40 mph.
But, WOW, it worked really well. My ears were a bit cool to the touch at the end of the ride, but were nowhere near as cold as I expected. And during the ride, the wool was very soft and comfortable.