## Common ground
All options are drainage or cleanout covers and frames, used to seal access points in plumbing or drainage systems.
## Options at a glance
**3926.90 – Plastic material**
- **Defining trait:** Made from synthetic polymer (plastic), typically lightweight and corrosion-resistant.
- **Typical examples:** HDPE or PVC covers for sewer cleanouts, garden drain grates.
- **Best fit when:** Corrosion resistance, low weight, or cost-effectiveness is key; common in residential or outdoor use.
**7325.10,7325.99 – Iron or steel**
- **Defining trait:** Made from ferrous metal, usually coated or galvanized to resist rust.
- **Typical examples:** Heavy-duty manhole covers, industrial drain frames.
- **Best fit when:** High load-bearing capacity or durability in harsh environments is required.
**7508.90 – Nickel**
- **Defining trait:** Made from nickel or nickel alloys, highly resistant to corrosion and heat.
- **Typical examples:** Specialized covers for chemical plants or marine environments.
- **Best fit when:** Extreme corrosion resistance or high-temperature performance is needed; rare in standard drainage.
**7616.99 – Aluminium**
- **Defining trait:** Made from lightweight, non-ferrous metal with good corrosion resistance.
- **Typical examples:** Lightweight cleanout covers for commercial buildings, rooftop drains.
- **Best fit when:** Weight is a concern, or moderate durability with easy handling is needed.
## Key differences
| Feature | Plastic | Iron/Steel | Nickel | Aluminium |
|------------------|---------------|----------------|----------------|----------------|
| Weight | Light | Heavy | Medium-heavy | Very light |
| Corrosion resistance | Good | Moderate (if coated) | Excellent | Good |
| Load capacity | Low to medium | High | High | Medium |
| Common use | Residential | Industrial | Specialized | Commercial |
## How to choose
- Is the cover used in a corrosive or high-temperature environment? → 7508.90
- Does it need to support heavy loads (e.g., roads, parking)? → 7325.10,7325.99
- Is weight or ease of handling critical? → 7616.99
- Is cost and general-purpose use the priority? → 3926.90
## Overlaps & pitfalls
A cover may combine materials (e.g., aluminum frame with plastic insert), but the primary material determines classification. Nickel and aluminum both resist corrosion, but nickel is far more expensive and used only in extreme conditions. If unsure, prioritize the **main structural material**