Polymaker PolyDryer Box vs SUNLU S4 Four-Spool Filament Dryer
Head-to-head spec comparison to help you pick the right environment upgrade for your needs.
Polymaker
$55
SUNLU
$169
Spec-by-Spec Comparison
| Spec | Polymaker PolyDryer Box | SUNLU S4 Four-Spool Filament Dryer |
|---|---|---|
| Category | Dry storage | Filament dryer |
| Role | Sealed spool storage | Multi-spool drying station |
| Max Temp | 0 C | 70 C |
| Capacity | 1 spool | 4 spools |
| Active Heat | No | Yes |
| Active Airflow | No | Yes |
| Humidity Readout | Yes | Yes |
| Print Through | Yes | Yes |
| Ventilation | No | No |
| Resin Workflow | No | No |
| Abrasive Ready | No | No |
| Best Materials | Stored PETG, nylon, TPU | PETG, TPU, nylon, PLA+ |
| Footprint | Stackable dry box | Large bench station |
| Price | $55 | $169 |
| Rating | 8.7/10 | 9.1/10 |
| Buy on Amazon | Buy on Amazon |
Pros & Cons
Polymaker PolyDryer Box
Pros
- Better as a system component than a one-off box: dry a spool, seal it, label it, and keep it ready.
- Humidity visibility makes it easier to catch when desiccant or sealing habits have stopped working.
- Modular dry-box workflow is ideal for users who rotate specialty materials but do not print each one daily.
- Pairs naturally with active dryers instead of trying to replace them.
Cons
- Dry storage is not active drying; a wet spool still needs a drying cycle before storage helps.
- Costs more than generic gasket boxes when you need to store many rolls.
- Capacity planning matters: one box per priority material adds up quickly.
SUNLU S4 Four-Spool Filament Dryer
Pros
- Four-spool capacity makes it the cleanest single purchase for AMS-style benches, color swaps, and households with several open rolls.
- Active heat plus circulation solves the two-part drying problem: warming the spool and moving humid air away from the filament surface.
- Print-through workflow reduces the chance that a dried nylon, TPU, or PETG spool immediately reabsorbs moisture while a long job runs.
- The higher price is easier to justify when you would otherwise buy two single-spool dryers plus separate dry boxes.
Cons
- Overkill for a one-printer PLA bench where a sealed storage box and occasional single-spool dryer would do the job.
- Large footprint demands a real bench position, not a corner shelf.
- Multi-spool dryers do not replace labeled dry storage; partial rolls still need sealed long-term storage after the print.
Our Verdicts
Polymaker PolyDryer Box
The Polymaker PolyDryer Box is the cleanest answer for users who already understand that drying and storage are different jobs. It is less exciting than a heated dryer, but it is often the missing step that keeps a fixed PETG or nylon problem from coming back two days later.
SUNLU S4 Four-Spool Filament Dryer
The SUNLU S4 is the best launch pick for a printer owner who has moved past one open PLA roll and now needs an actual humidity-control station. It is not the cheapest way to dry a spool, but it is the most coherent way to keep several filaments usable, print from the box, and stop treating wet PETG or nylon as a printer-tuning mystery.