## Common ground
All options refer to turbine housings used in engine systems to direct and manage high-pressure gases.
## Options at a glance
**8411.91 – Turbojet/Turbopropeller housing**
- **Defining trait:** Designed specifically for turbojets or turbopropellers in civil aircraft engines.
- **Typical examples:** Housing from a turbojet engine in a commercial airliner, turbine casing in a turboprop engine.
- **Best fit when:** The product is part of an aircraft propulsion system using jet or propeller-based turbines.
**8411.99 – Gas turbine housing**
- **Defining trait:** Used in general gas turbines, including industrial or power generation units, not limited to vehicles or aircraft.
- **Typical examples:** Housing in a stationary power plant gas turbine, turbine casing for marine propulsion.
- **Best fit when:** The product is used in non-automotive, non-aircraft gas turbine applications.
**8414.90 – Turbocharger housing**
- **Defining trait:** Specifically designed for automotive or marine turbochargers that boost engine intake pressure.
- **Typical examples:** Housing from a diesel truck turbocharger, turbocharger casing in a sports car engine.
- **Best fit when:** The product is part of a forced-induction system in internal combustion engines.
## Key differences
| Feature | 8411.91 (Aircraft) | 8411.99 (General Gas Turbine) | 8414.90 (Turbocharger) |
|-----------------------|--------------------|-------------------------------|------------------------|
| Application | Civil aircraft | Industrial/power plants | Automotive/marine |
| Primary use | Jet propulsion | Power generation | Engine boosting |
| Pressure/temperature | Very high | High | High (but lower than jet) |
## How to choose
- Is it used in a civil aircraft engine? → 8411.91
- Is it for a stationary or marine gas turbine (not vehicle-based)? → 8411.99
- Is it part of an automotive or marine turbocharger system? → 8414.90
## Overlaps & pitfalls
- A turbocharger housing (8414.90) may resemble a gas turbine housing (8411.99), but the application (vehicle vs. industrial) is key.
- Aircraft turbojets (8411.91) are a subset of gas turbines, but their use in civil aviation justifies separate classification.
- If unclear, prioritize based on **main function**: aircraft propulsion → 8411.91; engine boosting → 8414.90; power generation → 8411.99