Mechanically bonded mats (701914) are held together by physical entanglement or stitching of the fibers, while chemically bonded mats (701915) use a binder resin to hold the fibers in place. The bonding method is the primary classification criterion, so the manufacturing process documentation from the supplier is essential.

Glass wool and articles made from it fall under subheading 701980, which is distinct from the textile-type glass fiber products (yarns, rovings, woven fabrics) covered by the other subheadings. If the product is a finished insulation batt or roll made of glass wool, 701980 is the correct subheading.