My throat started to hurt again yesterday after spending most of the day out in the cold. So today I wore this:
Seems like a very good solution for -10C or colder. Breathing in warm air really warms your whole body and I didn't have cold hands today. There were several other people out there, mostly Swiss team xc skiers, with these masks on, so I wasn't the only one, but probably the slowest. Marc bought it for himself because he gets a cough when training in extreme cold and you can switch out the filter for another person and wash them after several uses.