Flax, true hemp (Cannabis sativa L.), and ramie are all bast fibers but are classified in their own dedicated headings (5301, 5302, and 5305 respectively). Heading 5303 captures jute and all remaining textile bast fibers not covered by those specific headings, such as kenaf and sunn hemp.

Heading 5303 covers fiber only up to the point just before spinning. Once the fiber has been spun into yarn, it classifies under the jute yarn heading in Chapter 53. Woven jute fabric moves further into the woven fabric headings of that chapter. The boundary is the spinning operation itself.