Since the buttons of the car keys have broken and the ones I did as substitution were not comfortable I decided to try to make new ones better and more functional.
Step 1: Materials and tools
To realize them you don't need much, just get or buy the oyumaru (it's the ideal material to create molds of things and objects you want to replicate) and Fimo (this is also a material that I didn't know and, as the oyumaru, I discovered thanks to other instructable authors who have reported them to me and recommended). As materials, you don't need any more. Just only a small pan, the oven and eventually a cutter.