4810.31 - Bleached uniformly throughout the mass and of which more than 95 percent by weight of the total fiber content consists of wood fibers obtained by a chemical process and weighing 150 g/m² or less:

This HTS category, 4810.31, encompasses bleached paper and paperboard that meets specific material and weight criteria. The paper and paperboard must be uniformly bleached throughout the mass. Crucially, over 95 percent of its total fiber content must consist of wood fibers obtained through a chemical process. Additionally, the material must have a basis weight of 150 grams per square meter (g/m²) or less.

This classification is distinguished from its siblings by its weight specification. Category 4810.32 covers similar bleached, chemically processed wood fiber paper and paperboard, but exclusively those weighing more than 150 g/m². Category 4810.39, "Other," serves as a residual category for kraft paper and paperboard within the broader scope of 4810.3 that does not fit the specific criteria of 4810.31 or 4810.32.

The subcategories within 4810.31 further refine the classification based on the physical form of the paper or paperboard. Subcategory 4810.31.10 specifically covers material presented in strips or rolls exceeding 15 cm in width, or in rectangular (including square) sheets where one side exceeds 36 cm and the other side exceeds 15 cm in the unfolded state. A further "Other" subcategory exists to capture material not meeting these specific dimensional criteria.