9902.01.29 - Silicon dioxide amorphous, certified by the importer as comprising entirely spherical micro-spheres with mean particle size of 28 to 45 micrometers (µm) and surface area 600 to 800 m²/g (CAS No. 7631-86-9) (provided for in subheading 2811.22.10)

This HTS category, 9902.01.29, specifically designates amorphous silicon dioxide characterized by its unique physical properties: spherical micro-spheres with a mean particle size ranging from 28 to 45 micrometers and a surface area between 600 and 800 square meters per gram. The importer's certification of these precise characteristics is a critical classification criterion, alongside the CAS number 7631-86-9. This provision is intended to cover specific forms of silicon dioxide that meet these exact specifications, likely due to their specialized applications or for temporary tariff purposes.

Distinguishing this category from its sibling categories within Chapter 99 is straightforward. The siblings in Chapter 99 are generally temporary provisions or temporary modifications related to trade agreements and section 22 import restrictions, covering a broad spectrum of goods. In contrast, 9902.01.29 is a highly specific temporary or special classification focused on a particular type of silicon dioxide, identifiable by its controlled particle morphology and surface area. The parent context of Section XXII highlights that this chapter contains provisions outside of the standard commodity classifications found in Chapters 1-97.

As this is a leaf node, there are no subcategories to introduce. Classification within 9902.01.29 is determined solely by the importer's confirmed compliance with the outlined physical specifications for amorphous silicon dioxide. Any silicon dioxide not meeting these precise particle size and surface area requirements, or not certified as such by the importer, would be classified under a different HTS provision, likely in Chapter 28.