You can re-use a key from another vehicle. You do need an "IT TESTER or aftermarket scantool" to program it in to the system. The Vehicle immobiliser downloads the logic code from the key as the logic code is fixed (same as Falcons for example) Vehicles like the Commodore have the code stored in the Body control Module and Upload the code to the "EMPTY" key/transponder, once writen the key will only work with that BCM. If you misplace your keys or they are stolen, you can erase that or all keys from the memory, DJKOR was correct in his statement Regards Phil