Cute as a button, these button-head hex screws are what we suggest for putting together a project with our slotted extruded aluminum. Use a 2.5mm hex wrench to attach/detach. This length is good for attaching something about 2mm/0.08" thick to 20x20 extrusion.
Comes in a pack of 50. M4 20 threads/cm (0.5mm pitch), 8mm threaded body.