We built the merinos to be the foundation and next to skin layers of your XKG hunting system. Construction consists of 19.5 micron 90/10 Merino Wool/Nylon at 260 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 Foundation 260 Merino ¼ Zip is assembled with a no-itch flatlock seam construction. It's material is ultra-breathable, moisture-wicking, and quick drying. With its natural fibers, it's also excellent at controlling odor. The Foundation 260 Merino ¼ Zip comes in Desert Shadow ®, Mountain Shadow ® and Olive Drab and outperforms other fabrics after several days in the field by repelling odor causing tendencies to keep you concealed. Paired with the Foundation Bottoms, the Merino Foundation pieces complete the base layer for the XKG Series. 19.5 Micron 260 Grams 90% Merino Wool 10% Nylon Chest Pocket Moisture Wicking Quick Dry 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: 10.8 oz.