The company says its ToughGard™ R, a rotary-based duct liner, "provides the best acoustical and thermal performance available in a duct liner for hvac systems." It features a tough, smooth, and damage-resistant airstream surface designed to "assure a long-lasting, efficient duct system with extended durability and service life." The duct liner is a flexible blanket composed of rotary-glass fibers bonded together with a thermosetting resin. A black composite, nonwoven mat and acrylic coating is bonded to the airstream surface, designed to give strength to the product.