This shirt is perfect for cool autumn days. The fabric is light and breathable. It absorbs moisture well. This is a great shirt for running or hiking. My son likes to wear it under his orange jacket on camping trips. I ordered it for my son on Wednesday. He usually runs between small and medium and it's just a little big for him. It's great for changing into a different shirt, but we had to go with a small one. For those who are between sizes, it may be best to go down a size. The fact that it's not skin-tight doesn't really bother him. Overall, there's really nothing about this shirt that my son wouldn't like. It's comfortable, lightweight and will keep you warm while you work.