PETG and TPU usually start looking wet before they start looking obviously ruined. Stringing gets worse, surfaces get fuzzier, extrusion sounds change, and prints start acting inconsistent enough that people blame slicer settings or the printer first. A lot of the time the spool simply sat out too long.
This is where the SUNLU S2 earns its lane. It is not the fancy answer. It is the cheap active-drying answer when one damp spool keeps muddying results and you want to recover it without pretending you need a bigger dual-spool box yet.
The current Amazon listing shows 4.4 out of 5 stars from 489 global ratings, which is enough buyer signal to treat the SUNLU S2 as an established cheap single-spool dryer rather than a speculative accessory pick.
Short answer
If PETG or TPU prints keep getting stringier, rougher, or more erratic after the spool has been sitting out, moisture is one of the first things to suspect. The SUNLU S2 is the cheap fix when the real problem is one active spool that needs straightforward drying more than it needs a nicer interface, storage-first workflow, or larger-capacity dryer.
What "printing wet" usually looks like
- extra stringing that keeps returning even after tuning retraction again
- popping or faint crackling during extrusion
- surface roughness, haze, or inconsistent top layers that were not there on a fresher spool
- TPU that feels more annoying to keep clean and predictable than it should
- PETG prints that start looking sloppier after the spool has been open for a while
If you need the diagnosis flow first, use the wet-filament guide. This page is the narrower lane for readers who already suspect moisture and want to know when a cheap active dryer is the honest next buy.
Why PETG and TPU create this exact problem
PETG and TPU are common enough that they sit on benches for long stretches, then get pulled back into service half-dry and half-forgotten. That is why they create so many false printer problems. They can still extrude, still sort of work, and still waste hours while looking like a settings issue.
For this exact failure mode, a low-cost one-spool dryer makes more sense than jumping straight to a premium box. The question is not whether you need a whole new filament workflow yet. It is whether you need to recover the spool that is already making today worse.
When the SUNLU S2 is the right fix
- one PETG or TPU spool is clearly acting worse after sitting out
- you want active drying and print-through convenience without spending much
- your bench still works mostly one active spool at a time
- the real need is moisture recovery, not two-spool backlog management or sealed long-term storage
That is why the deeper product read is the SUNLU S2 review, and the more direct buyer-fit page is the budget single-spool best-for article.
When something else makes more sense
If you want a cleaner mainstream step-up instead of the cheap fix, use the SUNLU S2 versus Creality Space Pi comparison. That is the better route when the real decision is budget lane versus nicer single-spool lane.
If your bigger problem is drying and then keeping that same spool sealed between sessions, the PolyDryer review is the stronger path. The SUNLU S2 is better when active recovery is the problem first.
If you are not even sure moisture is the culprit yet, the Govee H5075 review is the smarter checkpoint before you start buying around a false diagnosis.
What to check before you blame the printer
- Did this spool print better when it was newer or fresher?
- Did the stringing and roughness get worse after days or weeks out on the bench?
- Did the problem follow the spool more than the machine?
- Are PETG or TPU behaving worse while PLA still seems normal?
If the answer is mostly yes, you are usually closer to a moisture problem than a printer failure. That is exactly the lane where the SUNLU S2 is useful.
Editorial take
The SUNLU S2 works because it respects the boring version of the problem. One spool got damp. You want the cheap active fix. You do not need to turn that into a giant shopping project. For PETG and TPU owners stuck in that loop, this is one of the more honest Amazon buys on the whole site.
Should you buy it?
Buy it if one damp PETG or TPU spool keeps creating false printer drama and you want a low-cost one-spool dryer that can recover that spool without overcomplicating the workflow. Skip it if your real question is long-term sealed storage, nicer single-spool hardware, or larger-capacity drying.
Affiliate link: Check the SUNLU S2 on Amazon.
Common questions
Can wet PETG look like a settings problem?
Yes. That is one of the most common traps. PETG often gets stringier and rougher gradually enough that people start retuning before they question the spool.
Can wet TPU still print, just badly?
Yes. TPU often still prints, but with enough mess and inconsistency that it feels like the printer suddenly got worse when the spool is the real issue.
Is the SUNLU S2 enough if I only run one spool at a time?
Usually yes. That is the main reason it makes sense. It is a cheap active dryer for the common one-spool recovery problem.