Possible sub-categories for heat shrink tubes

Here are some possible sub-categories for heat shrink tubes:

1. Single wall heat shrink tubes
2. Dual wall heat shrink tubes
3. Thin wall heat shrink tubes
4. Medium wall heat shrink tubes
5. Heavy wall heat shrink tubes
6. Adhesive-lined heat shrink tubes
7. Non-adhesive heat shrink tubes
8. Colored heat shrink tubes
9. High-temperature heat shrink tubes
10. Low-temperature heat shrink tubes
11. UV-resistant heat shrink tubes
12. Flame-retardant heat shrink tubes
13. Heat shrinkable cable breakout boots
14. Heat shrinkable end caps

These sub-categories can vary based on the specific features and applications of the heat shrink tubes. 

Based on search engine data, some of the most popularly searched sub-categories of heat shrink tubes include:

1. Adhesive-lined heat shrink tubing
2. Dual-wall heat shrink tubing
3. Thin-wall heat shrink tubing
4. Heavy-wall heat shrink tubing
5. Colored heat shrink tubing
6. Flame-retardant heat shrink tubing
7. Medical-grade heat shrink tubing
8. High-temperature heat shrink tubing

However, the popularity of each sub-category may vary depending on the region and market. It's always a good idea to conduct some research on the specific target market and audience before creating product listings.