8420.91 - Cylinders:

HTS Code 8420.91 specifically covers cylinders that are designed as integral parts for calendering or other rolling machines, excluding those for metal or glass working. These machines are used in various industries for processes involving the application of pressure and heat through rotating cylinders to smooth, finish, or impart specific textures to materials such as textiles, paper, and plastic sheeting. The cylinders themselves are characterized by their smooth, often polished, surfaces and precise engineering to ensure uniform pressure and temperature during operation.

Distinguishing this category from its sibling, 8420.99, is crucial. While 8420.99 encompasses all other parts not specifically identified as cylinders, 8420.91 is exclusively for the cylindrical components themselves. This means that frames, gears, heating elements, or any other non-cylindrical part of a calendering or rolling machine would fall under the broader "Other" category (8420.99). The key differentiator is the physical form and function of the part as a cylinder within the specified machinery.

The subcategories under 8420.91 provide further granular classification based on the intended application of these cylinders. 8420.91.10.00 addresses cylinders used in machines for calendering or rolling textiles, such as those for finishing fabrics. 8420.91.20.00 applies to cylinders used in machines integral to the paper-making process, including the production of paper pulp, paper, or paperboard. Finally, 8420.91.90.00 serves as a residual category for cylinders used in other types of calendering or rolling machines not otherwise specified.