Using the lost-PLA method, this STEMFIE spanner is made of metal (brass). Like the lost-wax process, the original part was covered with plaster covering its surface except for a small sprue through which the molten metal flows.
The flask containing the plaster-concealed parts was then heated in an oven to burn out the PLA, leaving a void. After that, molten metal was poured into the plaster mold to form the metal parts.
Finally, the plaster was washed away, revealing the resulting STEMFIE parts. These were cut and sawed away from the sprue tree and then filed and brushed.