After more than 30 years in the outdoor media biz, I've become as skeptical about new technologies as you can get. When somebody tells me about fabrics and clothing that's supposed to keep you warm, cool, dry ... blah, blah, blah ... I take it with a pound of rock salt until I put it to use in the only real testing lab ... my own body in the great outdoors. To my great and extremely pleasant surprise I present this 37.5 Technology review. This stuff flat out works. 37.5 is a fabric technology designed to keep you dry and warm or cool as appropriate to the conditions. It does this by dealing with moisture vapor before it turns to sweat. I learned about it from the folks at Cocona at the Outdoor Press Camp in Park City, Utah. I know all about the pros ... and cons ... of wicking and layering, and Cocona's claims about what garments with 37.5 technology can do seemed too far outside the box to really work. Well, they handed me a long sleeve Carhartt Force Extremes shirt--dark grey, quarter zip-- and said, "Go try it." I'm a bigger guy and I sweat...the facts of my life. I put the shirt on, filled my Camelbak and headed out on a three-plus mile hike at about 7,500 feet elevation. The mountain sky was clear blue. Temperature was in the mid-80s. Terrain was steep in places. In the first quarter mile of the hike, I should have been soaked with sweat, hot and clammy. Yuck! But I wasn't! Not a bit! Not then nor for the rest of the hike we stretched over a couple hours and hydrating all the way. The 37.5 Technology incorporated in the fabric of the Carhartt shirt dealt with the water vapor my body was pumping out BEFORE it turned to liquid sweat. Absolutely amazing! I can't wait to do more testing with it in a variety of conditions, but I can't think of any that will be more difficult than what I put it through. By the way ... yes, 37.5 is an unusual name, but it is well-reasoned. From independent testing Cocona found that 37.5 degrees Celsius is the core temperature at which the human body performs most efficiently and a relative humidity of 37.5 percent is where human skin is most comfortable on the average. I don't know how I'd test that out myself, but now I have no reason to doubt them. I'm sold.