Vacuum Bags vs Dry Boxes for Filament: What Makers Say

The short answer

Vacuum bags suit spools in storage, and a dry box suits the spool you're printing. The difference is what happens during a print: a bag can't feed the printer, so the spool sits in room air, and Bambu Lab says freshly dried filament at about 55% RH can absorb enough moisture to affect print quality within 2 to 12 hours. Filament makers accept both. Prusa calls vacuum bags "another popular solution" as long as you "keep a desiccant in the bag," and Polymaker lists "airtight bags or dry boxes with desiccant, or use vacuum containers." SainSmart's eVacuum bags are closed bags with a valve, but their clear sides and humidity cards let you check humidity without opening them. Dry boxes such as Polymaker's PolyDryer Box and Prusa's Pro Filament Drybox have a filament outlet, and Bambu Lab's TPU guide recommends an AMS HT or a filament dry box for printing TPU. A bag takes less space. Neither one dries filament.

Ready to choose?

Who this guide is for

This guide is for anyone deciding between vacuum bags and a dry box for opened spools. It covers what makers say about each method, how you check the humidity inside, which ones let you print without opening them, and how many spools they hold. Our filament storage guide covers the basics of containers, desiccant types and labels. Our silica gel guide covers how much desiccant to use and how to recharge it. If a spool is already wet, read dryer vs dry box first, because storage doesn't fix it.

Filament storage: what to check before you buy ↗

What filament makers say about bags and boxes

Most filament makers don't pick one method. They describe a sealed space with desiccant and leave the container up to you. This is the storage method each maker names:

Maker	Container it names	Humidity it gives
Prusa Research	"a closed space or box, with some desiccant material in it." It also says "Another popular solution to keep your filament dry is using vacuum bags for storage. There are bags specific for filaments, but you can use any that will fit a filament inside. Keep a desiccant in the bag when storing the filament."	None given
Polymaker	"Once dried, keep your filament in airtight bags or dry boxes with desiccant, or use vacuum containers."	None given
UltiMaker	"a re-sealable bag with desiccant or a humidity-controlled storage system"	Below 50% RH for PVA, nylon and TPU 95A; "approximately 10–30%" for most of its materials
Bambu Lab (drying wiki)	"a sealed container or AMS with desiccants"	Most filaments stay dry for a limited time below 20% RH
Bambu Lab (TPU guide)	"Airtight storage boxes with desiccant" or "AMS HT for sealed storage"	"Store it with desiccant in an environment below 20% RH"
Overture	"A sealed or airtight container is ideal to prevent moisture exposure"	None given; storage temperature 15–25 °C

Bambu Lab's PLA Basic data sheet adds "(Sealed with desiccant)" to its under 20% RH storage figure. None of these makers says a bag beats a box or the other way round. Prusa and Polymaker are the only two here that suggest vacuum storage for opened spools. Our silica gel guide compares the humidity targets in more detail.

Several makers ship filament in a vacuum bag. Polymaker says each spool "is vacuum sealed in a bag along with a desiccant pack" after drying, and that the filament is ready to print "If the vacuum seal remains intact until opening." Overture says to use filament within a year "as it may no longer be vacuum-sealed or ideally stored." A factory bag is only a vacuum bag until you open it. After that, you need your own bag or box.

How each method keeps moisture out

Vacuum bags

SainSmart's eVacuum kit is the vacuum bag example in our catalog. SainSmart describes "Durable vacuum compression bags, heavy-duty valve, and double seal zipper for airtight protection." It says the "micro-porous vacuum bag enables maximum air removal," the zipper is "Reusable and resealable for frequent filament changes," and the valve is "Self-sealing." You remove the air with the included hand pump.

The weak points are the ones SainSmart lists in its own FAQ. If the bag "cannot be vacuumed or air leakage occurs after vacuum," it lists these causes:

The zipper isn't completely closed. SainSmart says to reseal it with the sealing clip.
The valve isn't on a flat surface, the pump isn't sitting flat on it, or you're pressing the pump too hard.
The valve isn't fully closed. SainSmart says to press it with your fingers after pumping.
The bag is damaged. SainSmart says to replace it.

SainSmart also says "Manual pumping is slow" and suggests squeezing out some air first. Expect to repeat this every time you put a spool back.

Dry boxes

A dry box keeps the air out with a lid seal rather than a vacuum. Polymaker says its PolyDryer Box "has the best sealing performance on the market," which is Polymaker's own claim, and the manual says to "replace the Airlocks tightly to ensure the best seal." Prusa describes its Pro Filament Drybox as a "sealed system" whose silica gel "actively absorbs moisture from the environment inside the box." Prusa lists that article as relevant for its HT90 printer.

Not every product sold as filament storage is sealed. Creality's Filament Storage Box page lists "Moisture-Proof and Damp-Proof" and "Magnetic Closure for Easy Access," but it doesn't describe a gasket, desiccant or hygrometer. Our PolyDryer Box vs Creality storage box comparison covers what each maker does and doesn't publish.

Desiccant in a bag vs a box

Both methods need desiccant. Prusa says to keep one in the bag, and Polymaker and UltiMaker both pair bags with desiccant. What changes is how it's packed:

SainSmart eVacuum kit: 15 desiccant packs for 10 bags. SainSmart doesn't say how many go in each bag, and it gives no way to recharge them. It says "If the humidity level rises above 50%, It is recommended to change the desiccants."
Polymaker PolyDryer Box: 30 g of color-changing silica gel in a combined hygrometer and desiccant box. The manual says "DO NOT place loose desiccant at the bottom of the PolyDryer™ Box."
Prusa Pro Filament Drybox: silica gel. Prusa doesn't give an amount in its Knowledge Base article.
Creality Filament Storage Box: none listed.

In the PolyDryer Box, the desiccant sits in its own container, and Polymaker's manual says to "Remove the desiccant box from the PolyDryer™ Box when filling or changing the desiccant." In a bag, the desiccant sits against the spool, and you have to open the bag and pump it down again to swap a pack. Our silica gel guide covers sizing and recharging.

How do you check the humidity without opening it?

Opening a bag to check it lets humid air in. These are the ways makers say to check:

Product	How you check	What the maker says
SainSmart eVacuum bags	A humidity card inside a clear bag	"Clear vacuum bags, together with cobalt-free humidity indicator cards enables you to have a quick view of the humidity level of your filaments without opening the bags." The cards read 10% to 60%.
Polymaker PolyDryer Box	Built-in hygrometer	"The minimum readout on the hygrometer is 10% - it will not display lower than that."
Prusa Pro Filament Drybox	Not described in Prusa's article	None
Creality Filament Storage Box	None listed	None

SainSmart's card tells you the humidity is at the spot that has turned grey, "between brown and light blue." Its 50% change point is well above the under 20% RH Bambu Lab gives for storage. If your filament maker gives a lower target, change the desiccant when the card passes that number, not SainSmart's.

Bambu Lab says "A hygrometer can be used to monitor the actual humidity level" in a sealed container. Our filament storage guide explains how to check whether a hygrometer is reading correctly.

Can you print from a vacuum bag or a dry box?

This is the biggest practical difference. A dry box with an outlet can feed the printer. A vacuum bag can't, so the spool is out in room air while you print.

Dry boxes that makers document for printing:

Polymaker PolyDryer Box. The manual says to "Feed the filament through the outlet plug and then place the spool in," and the Box comes with a 50 cm PTFE tube. Polymaker's wiki lists a replacement tube as "ID:4mm, OD:6mm." Polymaker's wet filament page says storage systems such as the PolyDryer "allow you to print directly from a dry environment."
Prusa Pro Filament Drybox. Prusa says "The box allows for storage and direct printing." You thread the filament through its white PTFE tube, load it into the printer, then push the tube into the opening.
Bambu Lab's TPU advice. Bambu says that because TPU is so hygroscopic, "the storage container used during printing must provide excellent airtightness," and recommends the AMS HT or a filament dry box. It says a dry box "provides a sealed, low-resistance environment for filament feeding," to use a spool holder so the spool turns smoothly, to feed from the box's side opening, and to raise the box so the filament feeds smoothly.
eSUN. Its eTPU-95A data sheet says "It is recommended to use it with eBOX cartridges when printing."

Polymaker goes furthest. For nylon, PVA, TPU and PETG, it says "often they need to be kept in a dryer even as they are being printed, especially in humid climates."

Vacuum bags. SainSmart describes no way to print from its bags. Its resealable zipper is for "frequent filament changes," meaning you take the spool out, print, and seal it again. UltiMaker says "Brief exposure to ambient air (for example, while transferring a spool from storage to a printer or Material Station) does not significantly affect filament quality, provided the material is returned to a dry environment promptly." Bambu Lab's figure is less forgiving for long jobs. It says that at about 55% RH, freshly dried filament can absorb enough moisture to affect print quality "within 2~12 hours, depending on how hygroscopic the filament type is." A long print from an open spool counts as more than brief exposure.

A feed tube adds drag. That matters most for flexible filament. Bambu's TPU advice above is about keeping that drag low, and our TPU compatibility guide covers feeding soft filament.

Capacity and space

Product	Capacity the maker gives	Size the maker gives
SainSmart eVacuum kit (1-spool size)	One spool per bag, 10 bags per kit. SainSmart's bag size line covers both sizes and says "It can be adapted to 0.5KG/0.75KG/1KG package of 1.75mm/2.85mm/3mm filaments," without saying which weights fit which size.	Bag 30 × 40 cm (11.81 × 15.75 in). SainSmart also offers a 40 × 40 cm size option it lists for 2 spools.
Polymaker PolyDryer Box	"Supports up to 1kg." Maximum spool 205 mm across × 78 mm, filament with spool.	235 × 120 × 235 mm
Polymaker PolyDryer Box XL	"Supports up to 3kg"	Not given on the pages we used
Creality Filament Storage Box	The page text says "Large Storage Capacity." Our comparison found a 10 kg figure in Creality's product images.	Not published

Bags are the compact option. Once the air is out, a bag takes up little more space than the spool. A dry box holds its shape whether it's full or empty, but you can see the spool and the hygrometer at a glance. Measure your spools before buying a box. Polymaker's 78 mm width limit includes the spool.

Does a vacuum bag or dry box dry filament?

Storage slows moisture uptake. It doesn't remove water that's already in the filament. The PolyDryer Box heats only when it sits on Polymaker's separately sold Dry Dock. Neither SainSmart nor Creality lists a heater for these products. Prusa recommends pre-drying filament "in a professional dryer" before it goes into its Drybox the first time. See dryer vs dry box if a spool already pops or strings.

How to choose between them

These are trade-offs, not a ranking. Pick by how you use each spool.

A vacuum bag fits if:

The spool is going into storage between jobs, not onto the printer.
You have many spools and little shelf space.
You're happy to pump the bag down each time you put a spool away.
You want to read the humidity through the bag without opening it.

A dry box fits if:

You print long jobs from moisture-sensitive filament, such as TPU, nylon or PVA, and want it sealed while it feeds.
You want a hygrometer reading in real numbers.
You want the desiccant in its own holder rather than loose against the spool.
Your spools fit the box's published size limit.

Many people use both. Spools you aren't using go into bags, and the one you're printing goes into a box.

Storage products in our catalog

Each product below comes with its maker's own instructions. None of them dries filament.

SainSmart eVacuum filament storage kit

Ten clear vacuum bags with a hand pump, 15 desiccant packs and 15 humidity cards that you read through the bag. SainSmart gives no way to recharge the packs, so plan to replace them.

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 Details checked 2026-10-06 against the manufacturer. Price and availability are on Amazon.

Polymaker PolyDryer Box

A sealed single-spool box with a hygrometer, 30 g of color-changing desiccant, airlocks and an outlet with a 50 cm PTFE tube, so you can print from it. Polymaker gives a maximum spool size of 205 × 78 mm.

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 Details checked 2026-10-06 against the manufacturer. Price and availability are on Amazon.

Creality Filament Storage Box

A storage box with a magnetic closure for keeping spools together and out of the way. Creality's page lists no seal, desiccant or outlet, so seal moisture-sensitive spools in a bag before you shelve them.

Creality

Creality Filament Storage Box (10 kg two-tier storage cabinet, unheated (SKU 4005010089))

Best for: Organizing up to 10 kg of spools out of dust near the printer.
Skip this if: You need airtight storage for nylon, PETG, TPU or other moisture-sensitive filament.

Specs, strengths, and limitations

Capacity: 10 kg on a two-tier rack (Creality image text); Creality's images show five spools per tier
Maker notes: Creality store SKU 4005010089. The Amazon model number (AMUS-CU-3D-AC-Storage Box-New) does not contain the SKU; brand, title and 10 kg capacity match. Creality image text: two-tier rack, 'Strong Load-Bearing without Deformation' with '10KG'; an 'Easy Installation' image shows the rack in parts. Creality image text: cover layers are Oxford cloth / support plate / Oxford cloth; 'Magnetic Closure for Easy Access'; 'Transparent and Visible' windows. Creality markets it for filament and UV-sensitive resin storage. Creality's page lists no desiccant, hygrometer, gasket seal, or outer dimensions. The Amazon listing says the rack is aluminium alloy; Creality's page does not state the rack material. Not the heated version: Amazon also lists a Creality 10 kg box with a 70 °C heating module (B0GYC85LFS), which is a different product.

Strengths

Manufacturer states the two-tier rack holds 10 kg of filament.
Manufacturer states the door uses a magnetic closure and the cover has clear windows.
Manufacturer states the cover is a three-layer Oxford cloth and support-plate construction.

Limitations

It is a fabric cabinet with a magnetic door, not a gasket-sealed box; Creality lists no desiccant or hygrometer, so it is better for dust and light than for keeping filament dry.
Storage only: it does not heat and will not dry wet filament.
Creality does not publish outer dimensions on its product page.

View on Amazon Details checked 2026-10-06 against the manufacturer. Price and availability are on Amazon.

Quick checklist

Check your filament maker's storage advice and humidity target, if it gives one.
Put desiccant in whichever container you use. Prusa and Polymaker pair both bags and boxes with desiccant.
With a vacuum bag, close the zipper fully, press the valve shut after pumping, and replace a bag that won't hold its vacuum.
Put a humidity card or hygrometer where you can read it without opening the bag or box.
Change the desiccant when the humidity passes your filament maker's target, not just the bag maker's.
For long prints with moisture-sensitive filament, use a box with an outlet so the spool stays sealed while it feeds.
Keep the feed path short and smooth, especially for TPU.
Measure your spools against a box's published size limit before you buy.
Dry wet filament first. Neither a bag nor a box will dry it.

How this guide was checked

This is a research-based guide. We haven't tested these bags or boxes for it. Every statement comes from the makers' Knowledge Base articles, wikis, data sheets, manuals and product pages listed in the sources, retrieved on 2026-10-13. Where a maker describes its own product, such as Polymaker's sealing claim or Creality's "Moisture-Proof and Damp-Proof," we've labelled it as the maker's claim. Read more in our editorial standards.

Ready to choose? The filament storage gear shortlist lists the bags, boxes, desiccant and hygrometers we've checked against their makers' documentation.

Vacuum bags vs dry boxes for filament storage

Who this guide is for

What filament makers say about bags and boxes