SainSmart eVacuum Bags vs Polymaker PolyDryer Box

Who this comparison is for

This page is for anyone choosing between SainSmart's vacuum bag kit and Polymaker's single-spool dry box. We compare SainSmart's 1-spool kit (10 bags, 30 × 40 cm, SKU 101-91F-400) and the PolyDryer Box sold as "PolyDryer™ Box (Only Storage Box)," without the Dry Dock.

For the general case of bags against boxes, including what Prusa, Bambu Lab and UltiMaker say about each, read our vacuum bags vs dry boxes guide. This page sticks to these two products. For more storage products, see the filament storage shortlist, and for the PolyDryer Box against another box, PolyDryer Box vs Creality Storage Box.

How we compared them

This is a research-based comparison. Every detail comes from SainSmart's product page and from Polymaker's PolyDryer product page, user manual and wiki, all listed in the sources. We haven't stored or printed from either product, so there are no humidity readings of ours here. Where a maker praises its own product, such as Polymaker's "best sealing performance on the market," we label it as the maker's claim.

Neither maker publishes a test of how long its product holds a low humidity. Polymaker's FAQ gives humidity readings after drying on the Dry Dock, but that's a drying result, not a storage test, and SainSmart publishes nothing to compare it with. So there's no test table on this page.

Side-by-side specs

Storing spools vs printing from storage

This is the main difference between the two.

• SainSmart eVacuum bags. SainSmart describes storage only: a "micro-porous vacuum bag enables maximum air removal," a "Reinforced double zipper ensures an airtight seal," and the zipper is "Reusable and resealable for frequent filament changes." Nothing on the page describes a filament outlet. To print, you open the bag, take the spool out, and pump the bag down again when you put the spool back.
• Polymaker PolyDryer Box. The manual's quick start says to "Feed the filament through the outlet plug and then place the spool in," and the box ships with a 50 cm PTFE tube. For a replacement tube, Polymaker's wiki gives "ID:4mm, OD:6mm." Polymaker's wet filament page says modular storage such as the PolyDryer helps "allow you to print directly from a dry environment."

Polymaker's wet filament page also says nylon, PVA, TPU and PETG "often they need to be kept in a dryer even as they are being printed, especially in humid climates." Note that it says a dryer: the PolyDryer Box on its own doesn't heat. The same page lists "airtight bags or dry boxes with desiccant, or use vacuum containers" for keeping dried filament dry, so Polymaker names both kinds of storage. It also calls PLA "less likely to be affected," so taking a PLA spool in and out of a bag may be all you need.

Polymaker doesn't say which printers or feeders the box suits, and neither maker mentions Bambu Lab's AMS or any other multi-material system. We make no printer compatibility claim for either. Our vacuum bags vs dry boxes guide covers what Bambu Lab says about feeding TPU from a dry box.

Desiccant and how you reuse it

• SainSmart. The kit includes 15 desiccant packs for 10 bags. SainSmart doesn't say what the desiccant is, how much each pack holds, or how many go in a bag. It gives no way to dry the packs. It says "If the humidity level rises above 50%, It is recommended to change the desiccants." The humidity cards are reusable: SainSmart says they "can be reused after drying with an oven or hair dryer," but gives no temperature or time.
• Polymaker. The box comes with 30 g of color-changing silica gel, which you pour into its own desiccant box. Polymaker says it's orange when dry and dark green when wet, and that boxes from the first batch of PolyDryers use different colors. When most of it has turned dark green, the manual lists three ways to dry it: on the Dry Dock at power level 3 for "~8 hours" with no filament in the box, in an oven at 100–120 °C for 1–2 hours, or in a microwave on low power for 30 seconds, flipped, then another 30 seconds. For the oven and microwave, it says to take the silica gel out of the box and put it in a heat-resistant container. The manual also says "DO NOT place loose desiccant at the bottom of the PolyDryer™ Box."

So the PolyDryer's desiccant is meant to be dried and reused, with instructions. SainSmart's instruction is to change the desiccants, so with its kit plan on buying replacements once the 15 packs are spent. Our silica gel guide covers sizing and recharging desiccant in general.

Checking the humidity

• SainSmart. Each bag gets a cobalt-free humidity indicator card, and the bags are clear, so SainSmart says you can see "the humidity level of your filaments without opening the bags." The card covers 10%–60%. Each spot turns from brown to light blue as humidity rises past its number, and SainSmart says the reading is the spot that has turned grey, "between brown and light blue."
• Polymaker. The box has a hygrometer with a display. The manual says to replace its battery with a 1.5 V LR44 when the display fades. Polymaker's FAQ says "The minimum readout on the hygrometer is 10% - it will not display lower than that." The color-changing desiccant gives a second check.

Both bottom out at 10%. A card gives a reading in steps between its printed spots. A hygrometer gives a number. Neither maker states how accurate its readout is. Our filament storage guide explains how to check a hygrometer.

SainSmart's 50% change point is SainSmart's figure. If your filament maker gives a lower storage humidity, change the desiccant when the card passes that number instead.

Which spools fit

• SainSmart. The 1-spool bag is 30 × 40 cm. SainSmart says the bags fit a "0.5KG/0.75KG/1KG package of 1.75mm/2.85mm/3mm filaments," but it gives no maximum spool diameter or width. That sentence covers both bag sizes on the page, so SainSmart doesn't say which weights each size takes. The same page also offers a 40 × 40 cm size it lists for "2 spools." That's a different size option from the one on this page.
• Polymaker. The manual gives a maximum of "205 Ø *78(H) mm (Filament with spool)" and filament diameters of 1.75, 2.85 and 3.00 mm. The product page says "Supports up to 1kg." For bigger spools, Polymaker sells the PolyDryer Box XL, which it says supports up to 3 kg. The manual also says to use the included spool roller "when the edge of spool damaged."

Measure your spools before you buy either. For the PolyDryer Box, check the outer diameter and the width against 205 × 78 mm. For the SainSmart bag, SainSmart gives only the bag size, so a wide or cardboard spool's fit isn't documented. Unknown fit isn't fit.

Space and reuse

SainSmart calls its bags "vacuum compression bags" but gives no packed size, so we can't say how much shelf space a bagged spool takes. The PolyDryer Box is 235 × 120 × 235 mm, per Polymaker's manual. Polymaker says you can "Personalize with printable add-ons for hanging or connecting them together."

Both are meant to be used again and again. SainSmart's zipper is "Reusable and resealable," and its FAQ says to replace a damaged bag. Polymaker's wiki says "Right now we do not offer replacement components for the PolyDryer," and gives the specs for a replacement PTFE tube and power adapter, plus an example third-party hygrometer, instead.

Pumping takes effort. SainSmart's FAQ says "Manual pumping is slow" and suggests squeezing some air out first. It also lists the causes when a bag won't hold a vacuum: the zipper isn't fully closed, the valve isn't flat or fully closed, the pump isn't seated on the valve or is pressed too hard, or the bag is damaged. The PolyDryer Box has no pump. Polymaker's manual only asks you to refit its airlocks "tightly to ensure the best seal" after the box comes off the Dry Dock.

Drying later

The PolyDryer Box is the storage half of Polymaker's PolyDryer. Put it on the separately sold Dry Dock and the same box dries the spool, then goes back on the shelf. Polymaker says "With one drying dock you can add as many PolyDryer Boxes as you need so your next project is always ready to go." For the Dry Dock itself, see our SUNLU FilaDryer S2 vs PolyDryer comparison.

The SainSmart bags have no drying option. Dry a spool in a separate dryer, then bag it.

What each maker says it's for

• SainSmart. It says the kit "allows you to keep your filaments in tip-top shape with ease," with bags and a valve "for airtight protection."
• Polymaker. It describes the PolyDryer as "When drying meets storage" and says of the box, "You'll never have to break the seal again." The sealing comparison in "the best sealing performance on the market" is Polymaker's own claim.

SainSmart

SainSmart eVacuum Sealed Bags Filament Storage Kit (1-spool size: 10 bags (15.75 × 11.81 in), hand pump, 15 desiccants, 15 humidity cards (SKU 101-91F-400))

Best for

Sealing up to 10 single spools with a visible humidity card in each bag.

Skip this if

You want an electric pump or need bags for 2–3 kg spools.

Specs, strengths, and limitations

Capacity

10 bags, 15.75 × 11.81 in, one spool per bag (SainSmart '1 spool' variant)

Maker notes

SainSmart lists the '15.75"×11.81" (1 spool)' variant as SKU 101-91F-400; the Amazon model number is 400256525. Title, brand and contents match. SainSmart package list: hand pump × 1, vacuum bag × 10, sealing clip × 2, desiccant × 15, humidity indicator card × 15. SainSmart: micro-porous vacuum bags, reinforced double-seal zipper, self-sealing heavy-duty valve. SainSmart: cobalt-free humidity indicator cards with a 10%–60% range; spots change from brown to light blue as humidity rises. If humidity rises above 50%, SainSmart recommends changing the desiccants. SainSmart: the humidity indicator cards can be reused after drying with an oven or hair dryer. No regeneration method is given for the desiccant packs. SainSmart FAQ: manual pumping is slow; squeeze out some air before pumping. SainSmart also sells a larger 15.75 × 15.75 in (2-spool) variant (SKU 101-91F-VS4040), which is not this listing. SainSmart's line 'It can be adapted to 0.5KG/0.75KG/1KG package of 1.75mm/2.85mm/3mm filaments' follows both bag sizes and does not say which weights fit which size.

Strengths

• Manufacturer package list includes 15 humidity indicator cards so you can check humidity without opening the bag.
• Manufacturer states the bags use a double-seal zipper and a self-sealing heavy-duty valve.
• Manufacturer states the indicator cards are cobalt-free and reusable after drying.

Limitations

• Storage only: the bags do not dry filament that is already wet.
• Kit includes a hand pump only; SainSmart's own FAQ says manual pumping is slow.
• SainSmart gives no regeneration method for the desiccant packs, only advice to change them above 50% humidity.

View on Amazon ↗ (opens Amazon in a new tab)Details checked 2026-10-06 against the manufacturer. Price and availability are on Amazon.

Polymaker

Polymaker PolyDryer Box (Single storage box, no Dry Dock (PX01003))

Best for

Keeping a dried 1 kg spool sealed and feeding it straight to the printer.

Skip this if

Your spools are wider than 78 mm or larger than 1 kg.

Specs, strengths, and limitations

Capacity

One spool up to 1 kg; maximum 205 mm diameter × 78 mm (filament with spool), per the PolyDryer user manual

Outer size

235 × 120 × 235 mm

Maker notes

Polymaker SKU PX01003 = PolyDryer Box (Only Storage Box); matches the Amazon model number. Manual packing list for the Box: PolyDryer Box, spool roller, 50 cm PTFE tube, hygrometer & desiccant box, 30 g colour-changing silica gel desiccant, 2 airlocks. The Dry Dock and power adapter are not included. Manual: Box product size 235(L) × 120(W) × 235(H) mm; maximum capacity 205 mm diameter × 78 mm (filament with spool). Desiccant turns from orange (dry) to dark green (wet). The manual says to regenerate it on the Dry Dock at power level 3 for about 8 hours (no filament in the box), in an oven at 100–120 °C for 1–2 hours, or in a microwave on low power for 30 seconds, flip, then another 30 seconds. Manual: 'DO NOT place loose desiccant at the bottom of the PolyDryer™ Box.' The hygrometer uses a 1.5 V LR44 battery; the Polymaker FAQ says its minimum readout is 10%. Filament diameters 1.75 / 2.85 / 3.00 mm. Manual: 'Feed the filament through the outlet plug'; Polymaker's image says 'Ready to print without ever opening the box.'

Strengths

• Manual has you feed the filament through the box's outlet plug and refit the airlocks tightly after drying, so you can print from the sealed box.
• Manual lists a built-in hygrometer and 30 g of colour-changing silica gel desiccant.
• Manufacturer states the box docks onto the separately sold PolyDryer Dry Dock for active drying.

Limitations

• Polymaker's manual lists a maximum spool size of 205 mm diameter × 78 mm, so wider spools will not fit.
• Storage only: it does not heat. Drying needs the separately sold Dry Dock.

View on Amazon ↗ (opens Amazon in a new tab)Details checked 2026-10-06 against the manufacturer. Price and availability are on Amazon.

Verdict: which should you buy?

The makers' own documents settle the main question. Polymaker documents printing from its box, and SainSmart documents only storage in its bags. If you need a spool to stay sealed while you print, choose the PolyDryer Box. If you need to keep many spools sealed between prints, choose the SainSmart kit, since one kit covers 10 spools where one PolyDryer Box covers one. Neither maker publishes a humidity-hold test, so we can't say which keeps filament drier. On desiccant, the PolyDryer has published regeneration steps and SainSmart has none. A common setup is both: bag the spools you aren't using and print from the box.

Choose the SainSmart eVacuum kit if…

• You want to seal up to 10 spools you aren't printing from right now.
• You want one kit with a bag, desiccant and humidity card for each spool.
• You're happy to pump a bag down each time you put a spool away.
• You want to read the humidity through the bag without opening it, and you'll buy new desiccant when it's spent.

Choose the Polymaker PolyDryer Box if…

• You want to print from a spool while it stays in a sealed box with desiccant.
• You want a hygrometer with a number and desiccant you can dry and reuse, with the maker's instructions.
• Your spools fit within 205 × 78 mm and weigh up to 1 kg.
• You may add Polymaker's Dry Dock later to dry spools in the same box.

Safety and limits

How this page was checked

Every detail above comes from SainSmart's product page and from Polymaker's product page, user manual, PolyDryer wiki page and wet filament wiki page in the sources section, retrieved on 2026-10-14. We haven't stored or printed from either product for this page, so there are no humidity readings of ours here. The SainSmart package list, bag sizes, humidity card range and FAQ come from SainSmart's visible product page text. The PolyDryer Box's size, spool limit, filament diameters, packing list, outlet and desiccant regeneration steps come from Polymaker's manual, and the regeneration steps match the product page FAQ and wiki; its 1 kg capacity, hygrometer minimum and warranty come from the product page FAQ and wiki. We didn't use product images or customer reviews. We searched both makers' pages and found no printer or AMS compatibility claim for either product, and no test of how long either holds a low humidity. Read more in our editorial standards and affiliate disclosure.

Filament storage: what to check before you buy ↗