Incredibly warm! Felted wool mittens for extra-cold days. Using the 3-layer principle, you would use the Ulvang Liner Glove first, then the Hammerfest Mitten as a midlayer and the Hammerfest Wind Mitten as the outermost, windproof layer. Hammerfest Mitten was in the equipment used in the 2011 expedition to the South Pole, with (among others) Vegard Ulvang.