9108.20 - With automatic winding:

This HTS subheading, 9108.20, specifically covers complete and assembled watch movements that feature automatic winding mechanisms. Automatic winding means the watch movement is powered by the kinetic energy generated from the wearer's natural motion, eliminating the need for manual winding. This category is distinct from its siblings, which cover electrically operated watch movements (which rely on a battery) and "other" watch movements that do not fit the criteria for automatic winding.

The subcategories under 9108.20 further refine the classification based on the number of jewels present in the movement. Subheading 9108.20.40.00 is for movements "Having over 17 jewels," a criterion often indicative of higher precision and durability in watchmaking. Conversely, subheading 9108.20.80.00 covers all other automatic winding watch movements that do not meet the "over 17 jewels" specification. This distinction is important for customs purposes as it can reflect varying levels of craftsmanship and value.