We built the merinos to be the foundation and next to skin layers of your XKG hunting system. Construction consists of 17.5 micron 100% Merino wool that weighs 150 grams which functions in any condition - keeping you cool in the heat with its breathability and warm in the cold with its tightly sewn fine wool fibers. The Merino 150 ¼ Zip is assembled with a no-itch flatlock seam construction. It's material is ultra-breathable, and moisture-wicking. With its natural fibers, it's also excellent at controlling odor. The Foundation 150 Merino ¼ Zip outperforms other fabrics after several days in the field by repelling odor causing tendencies to keep you concealed. Paired with the Foundation Bottoms and Beanie, the Merino Foundation pieces complete the base layer for the XKG Series. 17.5 Micron 150 Grm 100% Merino Wool Flatlock Stitched Seams Natural Odor Control Ultra Breathable No Itch Comfort Excellent Warmth to Weight Ratio ¼ Zip for Easy Pullover and Cool Off Shirt weight: 7.8 oz.