Prusa USS Drybox

The USS Drybox from Prusa is a compact, airtight storage solution that protects your filament from moisture and simplifies daily use. It mounts directly onto a spool holder, allowing you to draw filament without opening the box and simplifying spool storage. Ideal for anyone serious about print quality and material longevity.

Key Features

• Airtight construction in hydrophobic PP
• Mounts directly onto the spool holder
• Filament opening allows filament to be drawn without opening the box
• Minimizes internal volume to reduce humidity
• Stackable design for organizing multiple spools
• Helps keep filament dry and ready for printing

Moisture-Resistant Design

The USS Drybox is made from hydrophobic polypropylene (PP), a material significantly less permeable to moisture than common polycarbonate boxes. It performs well even without added desiccant. With its unique central opening, the box mounts directly onto a spool holder, reducing the free internal volume where humid air can accumulate.

Optimized for Daily Workflow

A key advantage of the Drybox is how seamlessly it integrates into your workflow. Instead of removing the spool for every print, you position it once and leave it there until the filament is used up. The rubber cap with a special opening holds the filament end, allowing you to draw filament without opening the box, which reduces exposure to humid ambient air. Because the box is stackable, organizing multiple spools becomes simple and efficient.

Reliable Filament Storage — Not a Drying Unit

The Drybox does not actively dry filament that has already absorbed moisture. Instead, it maintains a low-humidity environment, ensuring properly pre-dried filament remains ready for printing. For best results, it should be used as part of a workflow where filament is dried beforehand and then stored in the box.

Why It Matters

Moisture significantly affects the performance of many filament types, especially hygroscopic materials. By minimizing moisture absorption, you get more consistent prints with better adhesion, strength, and surface quality. The USS Drybox provides a practical and reliable system that preserves material quality, reduces preparation time, and integrates seamlessly into your daily setup.

Wet filament = ruined prints
When wet filament hits the hot nozzle, the water inside the material instantly boils and expands. This creates steam bubbles that are forced out of the nozzle, leading to stringing, oozing, and a rough surface instead of smooth walls.

No more problems with wet filament

Most filament storage boxes are just repurposed food containers. We developed the Prusa USS Drybox from scratch for 3D printing, made from special hydrophobic materials. It's a sealed storage container based on a simple idea: put the spool in the box, print directly from it, and leave it there until it's empty.

Unique quick access port

Access and load filament without opening the lid. The sealed port keeps moisture out during printing and fits a PTFE tube perfectly for direct connection.

Universal mounting

A clever central opening allows the box to be mounted directly onto your existing spool holder (Prusa bayonet spool holder). This also minimizes the free internal air volume where humid air can accumulate.

Stackable design

The flat sides allow the boxes to be stacked neatly. One box per spool: load the spool once and leave it there until the roll is empty.

Fits most spools

The box is large enough to accommodate standard spools from almost all brands (up to 1 kg) as well as smaller specialty spools.

Key figures

Why choose Prusa USS Drybox

• 95% less moisture absorption (vs. ambient air)
• 5× more airtight (vs. generic dryboxes, on par with museum quality)
• 50% better seal (vs. generic dryboxes)
• Stable for several weeks
• 10% relative humidity using 50 g silica gel

Moisture absorption over time

Measured with Prusament PCCF filament without silica gel in the box.

Why it matters
PCCF filament absorbs moisture quickly. At 0.12% water content, print quality deteriorates.

Museum-quality sealing

In addition to measuring moisture absorption over time, we tested the seal using the CO₂ decay method. By measuring how slowly a tracer gas escapes the container, we can precisely determine how often the air inside is replaced with humid air from the room.

While a common ziplock bag quickly leaks air, and even dedicated generic dry boxes struggle to maintain a complete seal, the Prusa USS Drybox is significantly more airtight. Its performance reaches a level of airtightness typically only required for museum display cases for preserving fragile historical artifacts. This means your filament remains in a controlled environment, protected from the outside world, for much longer than standard solutions.

Practical features

Prusa USS Drybox

• Integrated sensor
  Always in control of internal conditions. Built-in hygrometer and thermometer (°C/°F).
• Label holder
  Identify materials easily with included labels or 3D-print your own tags via a template from Printables.com.
• Smart side access
  Small side flaps allow for manual spool rotation or silica gel replacement without opening the entire box.

Frequently Asked Questions

Which spool holders are supported?
The Prusa USS Drybox fits perfectly on the bayonet spool holder of the Prusa CORE One+ and CORE One L. For CORE One, XL, MK4/S/+ and HT90, printable adapters are available (coming soon on Printables).

Can I print directly from it?
Yes. The sealed PTFE outlet allows the printer to pull filament with low friction while the internal environment remains airtight.

Is desiccant included?
Yes. There is space for 50 g of silica gel, which can maintain approximately 10% relative humidity (RH) for several weeks at a time.

Does it work with my non-Prusa printer?
You can feed filament directly from the box to any 3D printer. Mounting the drybox to the printer works with compatible spool holders, such as those on Prusa 3D printers (bayonet-lock spool holder) or other community-made spool holders for other printers.