At the Ishibutai 100, a snowy trail-running race in January 2023, this single layer was my basic outfit. When the wind picked up or at night I added a wind shell or Alpha Direct, and kept moving comfortably.
To get the most out of the fabric it feels best worn directly against the skin, but that isn't always practical, so I recommend wearing it over a dry layer.
Active insulation like Alpha Direct or Octa is good too, but in seasons too cold for it alone, or on windy days, Tilak's MERA HOODED is more comfortable. Colder still, I layer Alpha Direct over it.
