Sweat Block Technology No elastic to wear out. Works great under helmets. Dryline Fabric: High performance material quickly evaporates moisture so you stay dry and comfortable. Lightweight, durable, and abrasion resistant which will not lose shape. "Odor-free" VisaEndurance Fabric: Dryline fabric includes VisaEndurance, a microfiber polyester that has been embedded with SILVER IONS. These silver ions prevent the growth of bactreria. No bacteria. No smell. Product Care: Machine wash in cold and hang to dry.