9017.30 - Micrometers, calipers and gauges:

Category 9017.30 encompasses instruments designed for precise measurement of length and dimensions, specifically micrometers, calipers, and other general gauges. These tools are characterized by their handheld nature and their primary function of determining linear measurements with a high degree of accuracy. They are essential for quality control, manufacturing, and precision engineering applications where minute variations are critical.

This category is distinct from its siblings within heading 9017. While 9017.10 covers drafting machines and tables, and 9017.20 deals with broader drawing, marking-out, and calculating instruments, 9017.30 is narrowly focused on direct length measurement devices. Unlike 9017.80, which covers "other instruments" not otherwise specified in the heading, 9017.30 is reserved for those specifically designed for measuring length, and its subcategories further refine this scope.

Within 9017.30, two subcategories exist to further delineate specific types of instruments. Subcategory 9017.30.40.00 specifically covers micrometers and calipers, which are two of the most common and identifiable types of precision length-measuring tools. The remaining instruments that fit the general description of measuring length for use in the hand, but are neither micrometers nor calipers, are classified under the broader subcategory 9017.30.80.00.