As Shawn said, the very first 6105 were 24V and used a 42mm prop, we found later that a 45mm prop and 18V gave the same flow with less noise and lower power consumption. It is also possible the seller made a mistake and sent a wavebox power supply (identical but 24V) or bought a spare power supply which would have included a 12, 18V and 24V jumper. You can check the end of the prop, in the middle there will be a number 42 or 45 and this is the length in mm.