## Common ground
All options refer to combustion boats (a type of industrial furnace or vessel used for high-temperature processes), differing only in material composition.
## Options at a glance
**3926.90 – Made of plastic material**
- **Defining trait:** Constructed from thermoplastic or polymer-based materials, typically used in low-to-moderate temperature applications.
- **Typical examples:** Plastic-lined combustion chambers for small-scale heating units, non-load-bearing furnace components.
- **Best fit when:** The product operates below 200°C and is not exposed to direct flame or extreme thermal stress.
**6903 – Made of refractory ceramic**
- **Defining trait:** Engineered for high-temperature resistance (often >1000°C), used in structural furnace linings.
- **Typical examples:** Kiln walls, burner chambers in industrial furnaces, heat-resistant furnace bricks.
- **Best fit when:** The combustion boat must withstand continuous exposure to intense heat and thermal cycling.
**6909.1X – Made of ceramic**
- **Defining trait:** General ceramic material, may include non-refractory types; less specific than 6903 but still heat-resistant.
- **Typical examples:** Ceramic crucibles, lab-grade furnace boats, decorative or low-duty thermal components.
- **Best fit when:** The product is used in moderate heat environments (e.g., labs) and not designed for continuous industrial use.
**7017 – Made of glass**
- **Defining trait:** Transparent, non-metallic, and typically used in applications requiring visual monitoring or chemical inertness.
- **Typical examples:** Glass boats for lab-scale combustion analysis, transparent reaction vessels.
- **Best fit when:** The product must allow observation of internal processes and operates at low-to-moderate temperatures.
## Key differences
| Option | Material Type | Max Temp (approx.) | Thermal Shock Resistance | Primary Use Case |
|-------|----------------|--------------------|----------------------------|------------------|
| 3926.90 | Plastic | <200°C | Low | Non-structural, low-temp use |
| 6903 | Refractory ceramic | >1000°C | High | Industrial furnace structures |
| 6909.1X | General ceramic | 600–1000°C | Medium | Lab or moderate-duty use |
| 7017 | Glass | <500°C | Low (unless borosilicate) | Observation-based, inert environments |
## How to choose
- Does the product operate above 800°C? → 6903
- Is visual monitoring required? → 7017
- Is it used in a lab or low-temperature setting? → 6909.1X or 7017
- Is it made of plastic or polymer? → 3926.90
## Overlaps & pitfalls
- **Overlap:** 6903 and 6909.1X both cover ceramic materials; refractory ceramics are a subset of general ceramics. Use 6903 if high-temp structural use is intended.
- **Pitfall:** "Ceramic" (6909.1X) may include non-refractory types—don’t assume it’s heat-resistant unless specified.
- **Priority note:** If the product's main function is high-temperature structural integrity, prioritize 6903. Otherwise, choose based on material and use case