HTS code 9902.01.28 covers "Dioxosilane (Silicon dioxide amorphous) (CAS No. 7631-86-9) presented in the form of entirely spherical micro-spheres, certified by the importer as having a mean particle size of between 0.046 and 0.054 mm, uniform particle size with a uniformity coefficient of 1.65 or less and specific electrical resistance of 50,000 Ohm cm or more (provided for in subheading 2811.22.10)" 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.