Ultraviolet protection factor (UPF) 5 bluesign approved Twill sweatband Clip closure QuickDry 100% nylon ripstop / lining: 100% cotton sweatband Technology UPF Protection Designed for comfort and protection, this synthetic microfiber fabric offers an ultraviolet protection, blocking out harmful UV rays while promoting wicking and breathability for comfort in hot climates. UV radiation is an invisible part of sunlight associated with suntans, sunburns, premature aging, and skin cancer. The sun-protection properties of a woven or knit fabric are dependent upon the transmission, absorption, and reflection of UV radiation. The fiber type, dye, construction, and finished determine these characteristics. Our UPF-rated garments offer very good UV protection from prolonged exposure to the sun.