## Common ground
All options describe bursting discs—pressure-relief devices that rupture at a set pressure to protect systems.
## Options at a glance
**3926.90 – Plastic material**
- **Defining trait:** Made from non-metallic, synthetic polymer materials.
- **Typical examples:** Polyethylene or PTFE bursting discs for chemical or pharmaceutical systems.
- **Best fit when:** Used in corrosive environments where metal would degrade; low-pressure applications.
**7115.90 – Jewellery or precious metal**
- **Defining trait:** Contains or features decorative elements like gold, silver, or gemstones.
- **Typical examples:** Ornamental bursting discs in luxury equipment (rare).
- **Best fit when:** Product is primarily decorative; not a standard industrial use.
**7326.90 – Iron or steel**
- **Defining trait:** Constructed from ferrous metals, typically carbon steel.
- **Typical examples:** Industrial bursting discs in oil & gas pipelines or boilers.
- **Best fit when:** High strength and durability required; common in heavy-duty systems.
**7419.80 – Copper**
- **Defining trait:** Made from copper or copper alloys, offering good thermal conductivity.
- **Typical examples:** Bursting discs in HVAC or heat exchanger systems.
- **Best fit when:** Applications requiring corrosion resistance and thermal performance.
**7508.90 – Nickel**
- **Defining trait:** Made from nickel or nickel alloys (e.g., Inconel).
- **Typical examples:** High-temperature or highly corrosive environments (e.g., aerospace, chemical plants).
- **Best fit when:** Extreme conditions where standard metals fail.
**7616.99 – Aluminium**
- **Defining trait:** Made from lightweight aluminium or alloys.
- **Typical examples:** Bursting discs in food processing or aerospace systems.
- **Best fit when:** Weight reduction is critical; moderate pressure and non-corrosive environments.
## Key differences
| Option | Material Type | Corrosion Resistance | Strength | Typical Use Case |
|--------|----------------|------------------------|----------|------------------|
| 3926.90 | Plastic | High (non-metal) | Low | Chemical, low-pressure |
| 7115.90 | Precious metal | Varies | Low to medium | Decorative only |
| 7326.90 | Iron/steel | Medium | High | Industrial, high pressure |
| 7419.80 | Copper | Medium | Medium | Thermal systems |
| 7508.90 | Nickel | Very high | High | Extreme environments |
| 7616.99 | Aluminium | Medium | Low to medium | Lightweight applications |
## How to choose
- Is the disc made of plastic? → 3926.90
- Does it contain jewellery or precious metal? → 7115.90
- Is it made of iron, steel, or carbon steel? → 7326.90
- Is it made of copper? → 7419.80
- Is it made of nickel or a high-corrosion alloy? → 7508.90
- Is it made of aluminium? → 7616.99
## Overlaps & pitfalls
- **Overlaps:** A disc could be made of nickel *and* have a decorative coating (e.g., gold-plated), but the primary material determines the HS Code.
- **Pitfalls:** "Precious metal" (7115.90) is misleading—only applies if the disc is designed as jewellery or has significant ornamental value, not just a small plating.
- **Priority rule:** Use the **primary material** of the disc’s functional body. If unsure, prioritize structural material over decorative features