I needed an easy and fast printed spool for all the filament samples I've recently acquired (I am still quite new to all this and I want to test all the filaments I can get my hands on to). I didn't want to spend days printing, nor big amounts of filament. I also wanted it to be able to properly fit on a spool holder, not those tiny ones. So I designed my own.

1h 40min print time for the base, 50min for the lid. 27grams of filament total.

50mm inside diameter, 110 mm on the outside. Quite sturdy too.

Add-on design - print as many bases as you want as they snap to each other's back into a wider spool. You will only need one lid.

There is a hole at the bottom to easily fix the sample's end.

No screws are needed, no assembly, just an easy snap. You can add a dot of super glue if you have trouble fixing them together (I guess it depends on the printer's tolerance or print resolution, dunno really mine snapped pretty good). 

Well this is it, hope it helps someone.

HOW TO PRINT

I printed them in Prusament Recycled PLA (guess PETG will work too)

0.2mm layer
15% infill 

I've added a modifier to the bottom 2.5mm to disable top and bottom layers, add 4 perimeters, and select 15% Honeycomb infill (that's to enable the honeycomb pattern on the sides)