First Lite Glenbrook M ASAT MBGLNASMD Based upon a popular concept in mountaineering, cycling and backcountry skiing, the Glenbrook 3/4 Bottom is the perfect "tweener" base layer for crisp autumn mornings that are sure to get warmer as the day goes on. We married our top-shelf Merino Wool for odor mitigation with the incredible moisture wicking properties of our outerwear technology, 37.5 by Cocona, and created First Lite Aerowool. Anytime a premium is placed on moisture evacuation, during active hunting or hunting in warmer climates, Aerowool is your new go-to base layer.