So seriously, when weight, space, and breathability is an issue, and all you really want is something that can cut the wind, hold off mist or a light rain, and provide some early morning/late night insulation, then this windshirt is what should be in your pack. Yesterday I hiked nearly 50 miles through Pictured Rocks National Lakeshore. I carried a CamelBak Mule, so my supply space was quite limited before I even put in food or backup jacket. The Ion took virtually no space when considering it was a full length pullover jacket with hood, and weighed as much as an energy bar. My buddy and I started at 4am and finished at 7pm. The temps were dropping and the wind off Lake Superior was really picking up; so I threw on the Ion and then had to hike another 3 miles to the nearest town to hitchhike back to my truck. I heated-up pretty quick walking, but the Ion breathed great and my back didn't even accumulate sweat from being against the jacket and CamelBak. Mearly saying "Windshirt" doesn’t quite do this piece of gear justice. Its more like a Wind-Technical Shell.