According to the Uniform Mechanical Code, fittings for class 2, 3, and 4 ducts used in product conveying systems shall be no less than _______ that required for a straight duct run.

According to the Uniform Mechanical Code, fittings for class 2, 3, and 4 ducts used in product conveying systems shall be no less than _______ that required for a straight duct run.