## Common ground
Both options refer to pure alumina (aluminum oxide, Al₂O₃), a chemical compound used in industrial and technical applications.
## Options at a glance
**2818.20 – Pure alumina, not activated**
- **Defining trait:** Not treated to increase surface area or reactivity; retains a dense, stable crystalline structure.
- **Typical examples:** Alumina ceramics for electrical insulators, refractory bricks, grinding media.
- **Best fit when:** The product is used for structural, thermal, or insulating purposes without needing high surface reactivity.
**2818.30 – Pure alumina, activated**
- **Defining trait:** Chemically or physically treated (e.g., calcined at low temperatures) to increase surface area and reactivity.
- **Typical examples:** Catalyst supports, adsorbents, precursors for advanced ceramics, filler in composites.
- **Best fit when:** The product is used in catalysis, adsorption, or as a reactive precursor.
## Key differences
| Feature | 2818.20 (Not activated) | 2818.30 (Activated) |
|-----------------------|--------------------------|----------------------|
| Surface area | Low | High |
| Reactivity | Low | High |
| Primary use | Structural/insulating | Catalytic/adsorptive |
## How to choose
- Is the alumina used for insulation, wear resistance, or structural strength? → 2818.20
- Is it used as a catalyst support, adsorbent, or reactive precursor? → 2818.30
## Overlaps & pitfalls
A product may appear to fit both if it’s activated but still used structurally—however, the **main function** determines classification. If unsure, prioritize based on intended use: structural → not activated; chemical/functional → activated. The term “activated” refers to surface properties, not purity