I have a cheap electric screwdriver that I bought on amazon, and designed this model to hold two extra of bits on the back using some small magnets. You can get the magnets cheap on amazon. They seem to be 1.75mm thick with a 3mm diameter. The magnets and cap itself may friction fit depending on your printer and slicer settings. Mine did not, so I just used a little drop of hot glue to hold in the magnets and also glued the cap onto the screwdriver. Hope someone finds this helpful!