## Common ground
All options refer to cultured potassium chloride crystals, excluding optical uses unless specified.
## Options at a glance
**3104.20 – Fertilizers (small crystals)**
- **Defining trait:** Used as fertilizer in small, loose crystals under 2.5 g each, not in tablets or small packages.
- **Typical examples:** Granular potassium chloride for agricultural soil amendment.
- **Best fit when:** Product is sold loose, used in farming, and weighs less than 2.5 g per crystal.
**3105.10 – Fertilizers (tablets/small packs)**
- **Defining trait:** Same fertilizer use, but crystals are in tablets or packaged in units ≤10 kg gross weight.
- **Typical examples:** Pelleted potassium chloride for easy application; small bags for home gardeners.
- **Best fit when:** Product is pre-formulated into tablets or sold in small, sealed packages.
**3824.99 – Large crystals (non-fertilizer)**
- **Defining trait:** Crystals weigh 2.5 g or more, not used as fertilizer.
- **Typical examples:** Lab-grade crystals for chemical synthesis or industrial processes.
- **Best fit when:** Product is large, not intended for agriculture, and sold in bulk or by weight.
**9001.90 – Optical elements**
- **Defining trait:** Used as optical components (e.g., lenses, prisms) due to crystal clarity and refractive properties.
- **Typical examples:** Infrared optics or laser components made from high-purity crystals.
- **Best fit when:** Product is shaped for light manipulation, not chemical use.
## Key differences
| Feature | 3104.20 | 3105.10 | 3824.99 | 9001.90 |
|-----------------------|---------------|---------------|---------------|-----------------|
| Crystal size | <2.5 g | <2.5 g | ≥2.5 g | Variable |
| Form | Loose granules| Tablets/packs | Bulk/individual| Precision-cut |
| Primary use | Fertilizer | Fertilizer | Industrial/chem| Optical |
| Packaging limit | None | ≤10 kg | None | None |
## How to choose
- Is the product used in agriculture or soil treatment? → 3104.20 or 3105.10
- Is it in tablets or small packages (≤10 kg)? → 3105.10
- Are individual crystals ≥2.5 g and not for fertilizer? → 3824.99
- Is it shaped for light transmission/refraction? → 9001.90
## Overlaps & pitfalls
- A large crystal (≥2.5 g) used as fertilizer could fit both 3824.99 and 3105.10, but **use determines the code**: fertilizer use overrides size.
- Optical crystals must be clearly shaped for optics—purely chemical-grade crystals are not optical elements.
- If unclear, prioritize **main function**: fertilizer > industrial > optical