428 / | HD | STOCK MATERIAL OR MISCELLANEOUS ARTICLES |
221 | DF | WEB OR SHEET CONTAINING STRUCTURALLY DEFINED ELEMENT OR COMPONENT {9} |
304.4 | DF | .~ Composite having voids in a component (e.g., porous, cellular, etc.) {14} |
311.11 | DF | .~.~ Void-containing component has a continuous matrix of fibers only (e.g., porous paper, etc.) {2} |
311.51 | .~.~.~ Fibers of defined composition {1} | |
311.71 | DF | .~.~.~.~> Cellulosic {1} |