## Common ground
All options are electrically heated devices designed to warm vehicle seats.
## Options at a glance
**8516.29 – Control-equipped kit**
- **Defining trait:** Includes a control unit with electronic components (e.g., circuit board) for active temperature regulation.
- **Typical examples:** Factory-installed seat heaters with adjustable settings and digital controls.
- **Best fit when:** The product has a built-in thermostat or user-adjustable temperature settings via electronics.
**8516.79 – Heated throws & pads**
- **Defining trait:** Flexible, removable heating elements (often non-integrated) used on seats; typically plug-and-play.
- **Typical examples:** Portable seat covers with heating wires, heated car seat cushions.
- **Best fit when:** The heater is not permanently installed and can be easily removed or used on different seats.
**8516.80 – Resistance-based assembly**
- **Defining trait:** Uses electrical resistance (e.g., wire coils) to generate heat directly in the seat structure.
- **Typical examples:** Integrated seat heating elements stitched into car seat fabric.
- **Best fit when:** The heater is permanently built into the seat fabric or frame using resistive materials.
**8545.90 – Carbon/graphite heaters**
- **Defining trait:** Heats via carbon or graphite-based elements, known for fast, even heat distribution and thin profile.
- **Typical examples:** Thin, flexible heating layers made of carbon fiber or graphene used in premium seats.
- **Best fit when:** The product uses advanced carbon or graphite heating technology (not standard wire resistance).
## Key differences
| Feature | 8516.29 | 8516.79 | 8516.80 | 8545.90 |
|-----------------------|------------------|------------------|------------------|-------------------|
| Control unit | Yes (active) | No | No | No |
| Permanently installed | Yes | No | Yes | Yes |
| Heating element type | Electronic control | Flexible pad | Resistance wire | Carbon/graphite |
| Removable | No | Yes | No | No |
## How to choose
- Does it have a digital or electronic temperature control unit? → 8516.29
- Is it removable and used as a cover or pad? → 8516.79
- Does it use wire coils for heating? → 8516.80
- Is it made with carbon or graphite material? → 8545.90
## Overlaps & pitfalls
- A product with carbon heating and a control unit could fit both 8545.90 and 8516.29.
- 8516.79 may overlap with 8516.80 if the pad is permanently installed but uses resistance heating—priority should be given to **installation method** (removable vs. integrated).
- If no control unit or material type is specified, use **primary function and integration level** to decide