This little box helps you to pause printing when filament ends on the spoon.
You will need a switch (as shown on the photo). Connect it to printer using P-stop feature of Sailfish firmware. (https://groups.google.com/forum/#!topic/wanhao-printer-3d/iz3kDU7CQkY)
Just insert a little piece of filament when not used.
For 1.75mm filament.