37.5 Technology ExplainedUpdated a month ago

At First Lite, we believe your gear should work as hard as you do—and that’s why we’ve integrated 37.5® Technology into a wide range of our hunting apparel. This advanced material technology is designed to keep you in the ideal comfort and performance zone, no matter the conditions.

The name 37.5 comes from two key numbers:

• 37.5°C is the optimal core body temperature for peak physical performance.

• 37.5% humidity is the ideal microclimate next to your skin.

Staying in that zone means you perform better, feel more comfortable, and can hunt harder, longer.

How It Works:
37.5 Technology uses active particles derived from volcanic sand embedded into synthetic fibers. These particles attract and trap moisture vapor (before it turns into sweat) and move it away from your body. The hotter you get, the more efficiently it works—helping to regulate your body temperature in real time.

• Dries up to 5x faster than traditional synthetics

• Manages moisture before it becomes sweat

• Boosts breathability and energy efficiency during high-output hunts

• Performs even when you’re still, such as in a tree stand

From base layers and insulation to our breathable rain gear, 37.5 Technology adapts to your intensity level and the environment—keeping you drier, warmer, and more comfortable.

First Lite AeroWool® is a standout example: a powerful fusion of natural merino wool and 37.5-infused nylon, giving you the best of both worlds—natural odor resistance and advanced moisture management.

Whether you're on the move or waiting in silence, 37.5® keeps you dialed in and in the zone. That’s why we’ve made it the backbone of our system. Simply put, it’s the most effective fabric technology in the hunting world today.