I've used the Men's Kiln Quarter Zip from First Lite for approximately three months--in late-summer to early-fall conditions in Idaho. It is a thin, fairly lightweight layer that I don't wear alone when it is below 60 degrees. In that aspect I wish it was a little thicker and warmer. Hiking, it breathes very well, and regulates body temperature as advertised. My torso is a solid size medium, but my arms are long, so I ordered a large. That was a mistake, but I risked washing it and drying it on a typical machine-wash setting (machine wash warm, dry on high heat) and had just enough shrinking to make it fit well. The return policy on sizing was a little too much of a hassle, and I was planning on using it as soon as I received it, hence the risk of trying to shrink it slightly.