HTS code 9902.14.77 covers "Discs of drawn glass, each measuring between 1.4 m and 1.7 m in diameter, between 40 and 50 mm in thickness and between 200 and 250 kg in weight, the foregoing having been machined so as to render one surface concave in shape and the opposite surface convex in shape, the foregoing not framed or fitted with other materials and not designed to manipulate light to create an optical effect (provided for in subheading 7006.00.40)" under the US Harmonized Tariff Schedule. This is the official duty rate charged by US Customs when this product is imported into the United States, sourced directly from the U.S. International Trade Commission and refreshed daily.