Thin soft shell vest. Wore this over a skre wasatch baselayer and a kuiu 260 midlayer hiking in before sunrise at 14F. Plenty warm, worked up a bit of a sweat. Pack out at 50F with just the baselayer and I was sweating good. Took a bit to dry my sweat out of it but what can you do hiking 12 miles in the sun. Good piece of gear for late season if you're like me and the thinner blaze vests don't do anything for protection. Also worth noting I'm 5'11" 170lbs and fairly athletic. I typically wear medium but sized up for layering, fits great over layers.