This is a case for a variant of the quite wonderful universal transistor and component tester developed by Markus Frejek, and later Karl-Heinz Kübbeler. A full description of the project is available here: http://mikrocontroller.net/articles/AVR_Transistortester This case fits a kit sold by Banggood, see http://www.banggood.com/DIY-Meter-Tester-Kit-For-Capacitance-ESR-Inductance-Resistor-NPN-PNP-p-929603.html There is one version of the case bottom with holes for M3 countersunk screws. The other version is a pure snap lock, which I think works well enough. This version also has an internal structure that allows screws to be retrofitted. There are also two versions of the button; one with a collar that fits over the switch, and the alternative version with a flat bottom. Cases for variants with a larger graphical display are available here: http://www.thingiverse.com/thing:797733 and here: http://www.thingiverse.com/thing:694790Designed to be printed quite straightforwardly, without support and minimal cleanup needed. I used PLA. The button may be printed in a contrasting colour, It needs your first layer to be set up accurately if you want to avoid cleanup. If your first line prints to wide, you will need to cut a bit internally to make it fit the button. The standard version is entirely snap lock, so no extra hardware required. If you want to use screws, then it is best to use an M3 tap to create threads in the mounting holes of the top section.