## Common ground
All are laboratory appliances used for testing fuels, such as burners, reactors, or containers designed for high-temperature or chemical exposure.
## Options at a glance
**3926.90 – Made of plastic material**
- **Defining trait:** Resistant to low-to-moderate heat and chemicals; typically used for non-high-temperature fuel testing.
- **Typical examples:** Plastic fuel sample holders, disposable test vials.
- **Best fit when:** Testing fuels at room temperature or with minimal thermal stress, and disposability is preferred.
**6903 – Made of refractory ceramic**
- **Defining trait:** Withstands very high temperatures (over 1000°C) and thermal shock; used in combustion or pyrolysis testing.
- **Typical examples:** Crucibles for fuel ash analysis, high-temp burners.
- **Best fit when:** Fuel testing involves intense heat, such as in calorimetry or flame tests.
**6909.1X – Made of ceramic**
- **Defining trait:** General ceramic construction; may include non-refractory types with moderate heat resistance.
- **Typical examples:** Ceramic test tubes, sample dishes for low-to-medium heat.
- **Best fit when:** Moderate thermal or chemical exposure, but not extreme conditions.
**7017 – Made of glass**
- **Defining trait:** Transparent, chemically inert, and heat-resistant up to moderate temperatures; allows visual monitoring.
- **Typical examples:** Glass fuel burners, test tubes for combustion observation.
- **Best fit when:** Visual inspection during testing is needed and temperatures are below 500°C.
## Key differences
| Option | Material Type | Heat Resistance | Chemical Inertness | Transparency |
|--------------|---------------------|------------------|--------------------|--------------|
| 3926.90 | Plastic | Low | Moderate | Varies |
| 6903 | Refractory ceramic | Very high | High | Opaque |
| 6909.1X | Ceramic | Medium | High | Opaque |
| 7017 | Glass | Medium | Very high | Transparent |
## How to choose
- Does the appliance need to withstand temperatures above 800°C? → 6903
- Is visual observation during testing essential? → 7017
- Is it used for low-temperature or disposable testing? → 3926.90
- Is it a general-purpose ceramic device with moderate heat use? → 6909.1X
## Overlaps & pitfalls
- **Overlaps:** Some ceramic devices (6909.1X) may be refractory, but 6903 specifically denotes high-temperature resistance. Use 6903 only for extreme heat.
- **Pitfall:** "Ceramic" (6909.1X) is broader than "refractory ceramic" (6903); don’t confuse general ceramic with high-temp variants.
- **Priority note:** Choose based on the appliance’s MAIN function and operating conditions—heat resistance takes priority over material type