End cap and couplers for cardboard tubes from packing tape or bubble wrap rolls

This was a quick design I slapped together but it works well. As long as your cardboard tube has clean edges they should slip on. This will work with cardboard tubes from things like rolls of painters tape, packing tape, or bubble wrap. This can be used to make round containers of various sizes. You might be able to use them as end caps for shipping but I don't know how well they would hold up. I would be sure to use lots of tape if anything. I made a vented version as well with 5mm holes that are 5mm apart in a grid. Maybe use this to make a desiccant container?

Update 2-2-26: I added couplers to the design.

Models:

• Cardboard tube end cap: End cap with solid face.

• Cardboard tube end cap with vent holes : End cap with 5mm holes spaced 5mm apart.

• Cardboard tube end cap with vent holes : End cap with 2.5mm holes spaced 2.5mm apart.

• Wide open end cap edge protector: End cap that goes over edge of tube and protects it. Roughly 71.25mm opening. *Open middle coupler with 10mm high walls: Coupler with roughly 71.25mm opening in middle. Walls go up 10mm from center. 2.5mm gap between tubes.

• Open middle coupler with 15mm high walls: Coupler with roughly 71.25mm opening in middle. Walls go up 15mm from center. 2.5mm gap between tubes.

• Coupler with 2.5mm wall across middle: Coupler with no opening in middle. Walls go up 10mm from center. 2.5mm gap between tubes.

• 5mm hole vented coupler: Vented coupler 5mm holes spaced 5mm apart. Walls go up 10mm from center. 2.5mm gap between tubes.

• 2.5mm hole vented coupler: Vented coupler 2.5mm holes spaced 2.5mm apart. Walls go up 10mm from center. 2.5mm gap between tubes.

Dimensions: Outer Diameter: 88mm Inner diameter of cardboard tube ~76.25mm Wall thickness 2.5mm Bottom thickness 2.5mm Total height 12.5mm Gap thickness ~3.5mm

Videos explaining the design: https://www.youtube.com/watch?v=tVWgdEbPYPk

Category: DIY