Weather-Tight Container Caps and Couplers for Twist-Locking Prusament Spools

These NEW over-engineered Prusament spools are just so versatile! They normally assemble with bayonet-style twist-lock sides that require a 3D printable tool to open. 

This over-engineered lid system uses the spool's center hub (plus a couple o-rings) to securely lock valuables in a weather-tight compartment; something that is notoriously difficult for FDM printed containers. I also find my locking mechanism to be particularly satisfying, and find myself fidgeting with the containers pictured in this post; opening and closing them repeatedly.

You can even continue to use or reprogram the spool's OpenPrintTag for any sort of NFC tap & scan application. 

End-Cap Print Settings:

• Choose if you want a LITE or HEAVY DUTY version. The only difference is the outer hand-feel.

• Use PETG or other rigid filament (PLA may warp and loosen over time).

• Default 0.2mm layers works great! 

• No Supports!

NEW: (Optional) Coupler/Extender Print Settings:

• (same as above)

• LITE and MAX versions available. Only difference is height of outer rim and plastic used. 

• Enable Supports! - "On build plate only" - "Don't support bridges"

Weather-Resisting With O-Rings (Optional):

If you want water and weather resistance, these lids were designed to take a pair of 5233T352 High-Temperature Silicone O-Rings from McMaster-Carr. They are 60mm ID, 63mm OD, 1.5mm diameter. You must also apply a thin layer of grease (like that which came with your Prusa printer) for smooth operation. 

You may be able to use neighboring sizes of o-ring as long as the diameter is roughly 1.5mm. 

What about the sides of the spool?

• You can make a great pegboard! 

Updates:

14 April 2026: Now includes a rugged, weather-tight coupler for longer storage options! It is a bit more bulky than my slim extension ring, and 100% more water proof.