I had a fantastic time hanging out with SpikeT at the SCI Vegas show. While there he introduced me to a gentleman who has been dealing with Mike on a regular basis with his safari gear for his hunting concession in Zambia. (Sorry Mike, I don't remember the name of the company you buy your shirts through) The name of the clothing line is called "Diamondown", and it is friggin' amazing. Here in Missouri, we have been suffering from a unusual cold spell, and this stuff works. Diamondown is thin and lightweight, incredibly soft and comfortable to wear. In addition to wicking moisture away from the body, it blocks heat transfer. While at SCI and speaking to the designer of this fabric, (former NASA), he showed us a picture of a Navy Seal in infrared, who was wearing the top, but had wool on bottom. You could see the heat loss from everywhere but the top. I'm not much for a product plug, but on this one I have to. Check out their site, and make the investment. I have been a fan of wool for many years, but these undergarments work 10 fold better than wool. I personally like the fact that you can't be picked up by infrared sights, plus the fact that the critters can't see the heat transfer. It was well worth the investment.