## Common ground
All options refer to springs made from different metallic materials.
## Options at a glance
**7320 – Iron or steel**
- **Defining trait:** Made from ferrous metal, typically offering high strength and durability.
- **Typical examples:** Car suspension springs, mattress coils, industrial machinery springs.
- **Best fit when:** High load-bearing capacity and cost-effectiveness are needed.
**7419 – Copper**
- **Defining trait:** Made from copper or copper alloys, known for electrical conductivity and corrosion resistance.
- **Typical examples:** Electrical contact springs, precision instrument springs, vibration dampers in electronics.
- **Best fit when:** Conductivity, non-magnetism, or resistance to oxidation is essential.
**7508.90 – Nickel**
- **Defining trait:** Made from nickel or nickel alloys, valued for high temperature resistance and corrosion resistance.
- **Typical examples:** Aerospace components, high-temp engine springs, chemical processing equipment.
- **Best fit when:** Performance under extreme heat or corrosive environments is required.
## Key differences
| Feature | 7320 (Iron/Steel) | 7419 (Copper) | 7508.90 (Nickel) |
|---------------------|-------------------|-------------------|------------------------|
| Material type | Ferrous | Non-ferrous | Non-ferrous |
| Key property | High strength | Conductivity | Heat/corrosion resistance |
| Typical environment | General use | Electrical/precision | Harsh/industrial |
## How to choose
- Is the spring used in high-temperature or corrosive conditions? → 7508.90
- Does it need to conduct electricity or avoid magnetism? → 7419
- Is strength and cost-efficiency the main priority? → 7320
## Overlaps & pitfalls
A spring may combine properties (e.g., nickel alloy with copper content), but the primary material determines classification. If unclear, prioritize the dominant metal by weight or function. No option is inherently more correct—choose based on the material’s main role