This is a compact box for a single spare sparkplug. It fits exactly the old style sparkplugs with 14mm thread and 21mm hex drive.

I wanted one of those for each of my old mopeds and cars, it is always good to have at least one spare plug in the vehicle toolkit.To protect the porcelain insulator and the electrode this plug should be carried in a shockproof box.

The longer part has a hex shape inside and a knurling surface on the outside, so it can be used to insert the sparkplug to the cylinder thread and screw it hand-tight. The lettering on the outside says "Spark Plug" and "Zündkerze" (=german). Feel free to make changes for different sized sparkplugs. I'd like to see some makes ;-)

Edit 28.03.2018: I added a smaller, slightly different version, this fits for a small M10 / 16mm Hex drive spark plug, like the ones in the small 4-stroke engines (Honda Monkey, Dax etc.) This file is called "small_Zuendkerzenbox.stl"

Edit 07.02.2021: Added a longer version of the upper part for the bigger sparkplugs, because someone uses sparkplugs with the screwcap on top. This is unchecked and was not printed by now, I would appreciate any "makes" on this to confirm size and function!