I recently had someone give me a key exactly the same as my apartment key and wanted to make something that would differentiate them. This Transformers Autobot key cover is designed to be printed on an FDM printer with supports, 0.2 mm layer height, 10% infill. It fits one of those hex style house key heads. The two parts will need to be superglued together and then place the key in the slot. The hardest part about this is trying to pry the keyring open large enough for it to fit.