The Sol Cool™ Arm Sleeves are rated UPF 50+ for optimal sun protection, and have built-in cooling with Xylitol, which is infused into fabric fibers to create a cooling sensation on contact with moisture. They also feature silicone grips at the inside upper arms, thumb loops, and an elastic finger loops to keep sleeves secure. ExOfficio® loves innovation, and developed the new BugsAway® Sol Cool™ technology to give you the ultimate in travel comfort and protection. Cool and fresh: Sol Cool™ Xylitol knits react with moisture to create a cooling sensation, and SILVADUR™ activates silver ions in the presence of undesirable bacteria, helping eliminate odor. Bug blocking: BugsAway® apparel is treated with Insect Shield®, giving you invisible, odorless protection just by putting on your clothes. The treatment is bound to fabric fibers, so it stays in your clothes—not on your skin—and lasts through 70 washes. Ants, flies, chiggers, midges, and ticks don't like it, and neither do mosquitoes, which can transmit insect-borne diseases such as Zika, Chikungunya, Dengue, and West Nile viruses.