These are Allen keys from M3 to M5. I created them by measuring the actual keys. I wanted to test some Polycarbonate and its strength. They came out a bit beefier. So in order for them to fit perfectly in the hole you have to melt the tip of it and press it inside the corresponding bolt. You can customize their dimensions in customizer too. They are pretty tough. I can't hold a nut with my hands and tight it more. When tightening an M5 bolt on the MendelMax it slipped and didn't break in half. Also it needed less than 1/4-turn tightening with the actual Allen key. I consider it working and may try it with the other thermoplastics too. Comes in handy to have those keys always on the machine.