Polyester fleece is great stuff for an intermediate layer, an outer layer if not around sparks, and there are some varients that have a wind-blocking layer (otherwise they can be a bit porous in moderate to high winds). Fleece is even better than wool for wet performance. It is not as ultimately durable, but is plenty durable for most of us. I wear both (wool and fleece).<br><br>IMHO, 50-50 NyCo or 60-40 NyCo ("Mountain Cloth") is THE best overall performer for outer layer rough use in the outdoors. It is not all equal; depends on the weave (I think) - twill is not quite as resistent to wind as sateen in my opinion (and I am slowly testing that out).<br><br>I am not crazy about 50-50 Nylon-polyester, but it seems to work fine. As far as I know it is normally only found in what is a kind of twill. YMMV; but it seems to be good stuff, even if I am not crazy about it. There may be some brushed-finish poly mixes as well - lots of new stuff hitting the market lately.<br><br>FWIW, there is increasing use of 100% polester for shells - many of the Columbia products are using it, I think. The cordura-like weave is "noisy" compared to cotton blends, but it sure seems to perform well, and it should not be quite as vulnerable to sparks as nylon, altho I have yet to find out "the hard way".<br><br>100% nylon is now available in so many kinds of fabric that I'm reluctant to catagorize it. There are even "fleece-like" brushed nylon shells. It is the MOST vulnerable to sparks and, ultimately, to UV degradation (polyester much better resists UV, and of course the natural fibers best resist UV). That does NOT mean it will fall apart in a year - don't get me wrong. I have a couple of pairs of 100% nylon pants that are kind of like, ummm, imagine brushed poplin. Awesome in hot weather, but I would not care to have it against my skin in cold weather. Definately not as durable as NyCo or cotton-poly, but VERY lightweight and comfy. As a gross generalization, I think nylon shells tend to be "noisier" that others, but they are pretty darned good otherwise for performance. Keep away from sparks unless you crave the "pinhole weave" effect.<br><br>Now let me tell you what I have not yet found that I suspect would be the ultimate: NySi - like a 50-50 blend of nylon and silk. Doesn't that sound interesting? As I say, I have not found any yet...<br><br>Regards,<br><br>Scouter Tom