When First Lite engineered their Outerwear Collection, we looked closely at every fabric technology in existence. We had our pick of the litter, from better-known outerwear technologies to more niche, lesser marketed performance fabrics. The truth in outerwear manufacturing is that the brand in question can generally use whichever fabric they choose. The costs vary as does the performance, but if a brand is willing to pay for the best, they can choose to incorporate it into their offerings. First Lite chose 37.5 because third party empirical testing as well as extensive field use by our own employees left us greatly impressed by the superior performance of the fabric. The bottom line is that 37.5 breathes at a rate that is anywhere from 50% to 300% better than any of its competition, while offering waterproof levels that were within a 5% tolerance of our competition.
Our DNA is active, extremely vigorous mountain hunting. We are based in the Rocky Mountains and literally test our products year round in some of the steepest, most demanding terrain in North America. Breathability becomes paramount when you're climbing significantly steep, rugged slopes with heavy packs in less than ideal weather conditions. If you sweat under your outerwear and the fabric doesn't allow that moisture to escape, you might as well expose your base layers to the elements and skip the outerwear all together. 37.5 technology does the absolute best job of transporting that moisture from your base layers to the outside of the First Lite garment so that you can remain safe and dry while exerting yourself in the most brutal of weather conditions. This is why First Lite selected 37.5 Technology over other fabrics and has enjoyed award-winning products ever since.
The Science behind 37.5 Technology
Comfort in clothing is greatly influenced by the temperature and humidity next to skin known as the microclimate. For the average person, the body strives to maintain an ideal core body temperature of 37.5° C. You are most comfortable when the microclimate next to your skin has a relative humidity close to 37.5%. When you are in this ideal 37.5 comfort zone, you are also in your ideal performance zone. 37.5 technology helps your body manage the moisture in your microclimate to keep you in this "37.5 zone" of comfort and performance.
Your body already has the ultimate thermo-regulating system. The perspiration vapor that comes off of skin during activity cools the body when working hard. In fact, each gram of evaporated sweat releases 580 calories of stored heat. Unless this water vapor can be removed from the microclimate, it builds up in clothing, footwear, or gloves and creates a clammy and uncomfortable microclimate. 37.5 technology works to enhance the body’s natural cooling mechanism—the body puts out sweat to cool it down, 37.5 technology removes it from the microclimate.
With 37.5 technology, patented active particles permanently embedded at the fiber level capture and release moisture vapor. Not only do these active particles provide 800% more surface area to the fiber, they also provide a unique driving force to remove moisture vapor unlike any other technology. By actively responding to body heat, the active particles use this energy from the body to accelerate the vapor movement and speed up the conversion of liquid to vapor, significantly increasing drying rates. This means the hotter the user gets, the stronger the driving force removing moisture becomes—and the more comfortable the garment remains.
37.5 technology works to keep the optimum relative humidity in your microclimate so your body more efficiently maintains an ideal core temperature, enabling you to perform better, longer. Fabrics made with 37.5 technology dry up to five times faster than similar fabrics, diminishing wet cling. 37.5 technology is made with naturally derived materials so there are no harsh chemicals to irritate your skin. 37.5 active particles are permanently embedded into yarn and will never wash out or degrade.