Southwire cable tie/duct straps are the superior tie to use for HVAC installations. UL 181 B-C approved for use on flex duct. These cable ties are proudly MADE IN THE USA from a UV-resistant industrial strength Nylon 6/6. Perfect for supporting air ducts and other miscellaneous items that need to be tied together. 50-Pack, 36-inch black cable ties with 175lb tensile strength for EXTRA durability. Working temperature range: -40°C to 85°C or -40°F to 185°F. Rated for indoor and outdoor use. UL listed.