## Common ground
All options are types of laboratory muffles (insulated containers for heating samples) differing in material.
## Options at a glance
**3926.90 – Plastic**
- **Defining trait:** Made from heat-resistant plastic, suitable for low-to-moderate temperatures.
- **Typical examples:** Polypropylene or PTFE-lined muffle; used for acid digestion.
- **Best fit when:** Handling corrosive chemicals at temperatures below 200°C.
**6903 – Refractory ceramic**
- **Defining trait:** Made from high-temperature-resistant ceramic, often used in industrial furnaces.
- **Typical examples:** Alumina or silica-based muffle; withstands >1000°C.
- **Best fit when:** High-temperature calcination or ashing of samples.
**6909.1X – Ceramic (general)**
- **Defining trait:** Broad category of ceramic materials, not necessarily refractory; may include non-fireproof types.
- **Typical examples:** Glazed pottery muffle; used in low-temp labs.
- **Best fit when:** General lab use with moderate heat and no extreme thermal stress.
**7017 – Glass**
- **Defining trait:** Made from borosilicate or quartz glass, transparent and chemically inert.
- **Typical examples:** Quartz muffle for UV-sensitive reactions; used in spectroscopy.
- **Best fit when:** Need visual monitoring of reaction or high chemical purity required.
## Key differences
| Feature | 3926.90 (Plastic) | 6903 (Refractory ceramic) | 6909.1X (Ceramic) | 7017 (Glass) |
|---------------------|-------------------|----------------------------|-------------------|--------------|
| Max temp (~°C) | <200 | >1000 | ~500–800 | ~500 |
| Chemical resistance | High (acid/alkali) | Very high | Moderate | Excellent |
| Transparency | No | No | No | Yes |
## How to choose
- Does it need to withstand over 1000°C? → 6903
- Is visual monitoring required during heating? → 7017
- Is it used with strong acids or bases at moderate heat? → 3926.90
- Is it for general lab use without extreme heat or transparency needs? → 6909.1X
## Overlaps & pitfalls
- **6903 vs 6909.1X:** Refractory ceramic is a subset of ceramic; if the muffle is rated for high temp, prioritize 6903.
- **Plastic vs glass:** Both resist chemicals, but plastic fails at higher temps—don’t confuse "chemical resistance" with "thermal stability."
- **No priority rule given:** Choose based on the product’s MAIN function—e.g., high-temp use → 6903; transparency → 7017