## Common ground
All options are types of combustion tubes used in laboratory or industrial settings for high-temperature reactions.
## Options at a glance
**3926.90 – Plastic material**
- **Defining trait:** Resistant to low-to-moderate heat but not suitable for sustained high temperatures.
- **Typical examples:** Low-temp lab tubing, disposable sample holders.
- **Best fit when:** Used in non-combustion or low-heat applications (e.g., gas flow guides).
**6903 – Refractory ceramic**
- **Defining trait:** Designed to withstand extreme heat and thermal shock; often used in continuous high-temp processes.
- **Typical examples:** Furnace components, kiln tubes, industrial combustion chambers.
- **Best fit when:** Operating above 1000°C or in harsh thermal environments.
**6909.1X – Ceramic**
- **Defining trait:** General ceramic material; may include non-refractory types with lower heat resistance.
- **Typical examples:** Insulating tubes, low-temp lab fixtures.
- **Best fit when:** Moderate temperature use (below 800°C), not for sustained combustion.
**7017 – Glass**
- **Defining trait:** Transparent and chemically inert but fragile and limited to moderate temperatures.
- **Typical examples:** Reaction vessels, visual inspection tubes, low-temp burners.
- **Best fit when:** Need visibility during reaction or use below 500°C.
## Key differences
| Feature | 3926.90 (Plastic) | 6903 (Refractory ceramic) | 6909.1X (Ceramic) | 7017 (Glass) |
|---------------------|-------------------|----------------------------|-------------------|--------------|
| Max temp | <200°C | >1000°C | ~800°C | ~500°C |
| Thermal shock | Poor | Excellent | Moderate | Poor |
| Transparency | No | No | No | Yes |
| Chemical resistance | Low | High | Medium | High |
## How to choose
- Does it need to withstand sustained high temperatures (>800°C)? → 6903
- Is visibility during reaction important? → 7017
- Is it used in low-heat or disposable applications? → 3926.90
- Is it ceramic but not specifically refractory? → 6909.1X
## Overlaps & pitfalls
- **Overlap:** 6903 and 6909.1X both involve ceramics; refractory ceramic is a subset of ceramic. Use 6903 only if high heat resistance is critical.
- **Pitfall:** "Ceramic" (6909.1X) may include non-refractory types—don’t assume it’s heat-resistant.
- **Priority:** Choose based on the product's MAIN function: if for extreme heat, pick 6903; if for visibility, pick 7017