All No Fly Zone socks are manufactured using yarns treated with permethrin insect repellent. Odorless and durable, permethrin repels common biting insects like mosquitoes, flies, chiggers, midges, ticks, and ants. And best of all, it doesn’t alter the amazing qualities of our 100% US-made merino wool. Wearing the No Fly Zone Boulder lowers your chances of getting bothersome bites - or worse, insect-borne diseases - on your next day hike or backpacking trip. Fit & Design: Cushion that is light in weight along the base of the foot only Highly versatile, all-season construction Traditional sock height that fits firmly on the lower calf, also known as the daily Advanced knitting techniques create a totally flat connection in the toe box, reducing bulk and eliminating blister-generating friction Reinforced construction and low-stress seam placement reduce wear and tear, increasing the life of the sock Additional Details: Merino wool is soft, itch-free, naturally odor- and bacteria-resistant, cool in the summer and warm in winter Farm To Feet sources their 100% U.S. grown merino wool exclusively from sheep raised by American farmers on American farms