9902.11.91 - Plug-type closures of polyethylene, suitable for use in capping specimen tubes and measuring 15 mm in length; each closure having an upper portion designed to extend beyond the specimen tube to permit holding of the closure, such upper portion having a diameter of 15.5 mm and thickness of 3.3 mm and having a notched groove; with the bottom portion of such closure designed for insertion into a specimen tube having a diameter measuring approximately 11.7 mm; the foregoing closures certified by the importer as for use in an automated insertion system (provided for in subheading 3923.50.00)

This HTS category, 9902.11.91, specifically classifies plug-type closures manufactured from polyethylene. These closures are designed for a very particular application: capping specimen tubes within an automated insertion system. Key physical characteristics that define these closures include a length of 15 mm, an upper portion extending beyond the tube with a 15.5 mm diameter and 3.3 mm thickness, featuring a notched groove for handling, and a bottom portion designed for insertion into a specimen tube with an approximate diameter of 11.7 mm. The crucial determining factor for classification under this heading is the importer's certification that these closures are intended for use in an automated insertion system, as provided for in subheading 3923.50.00.

Distinguishing this category from its siblings at the same level, which primarily cover live animals and a vast array of other general merchandise, is its highly specific nature. Unlike broader classifications for general plastic articles or even more specific closures, 9902.11.91 is reserved for closures with precise dimensions and a certified application within a specialized automated system for specimen tubes. This specificity avoids misclassification with general-purpose stoppers, caps, or other plastic closures not meeting these stringent criteria.

As this is a leaf node within the HTS, there are no further subcategories branching from 9902.11.91. Therefore, the classification process for goods falling under this heading concludes with verifying that the imported polyethylene plug-type closures precisely match all the detailed physical and functional attributes described, including the critical certification for use in an automated insertion system. This ensures that these specialized closures are correctly accounted for within the customs framework.