Do you have a link to the reference so we could see them. I don't know if that is something special, but from what I know about props a 0x0 prop can't exist. In the discription for a prop the first number is the diameter of the prop and the second number is the pitch. For example, a 12x6 prop would be 12 inches in diameter with a pitch of 6. In your case a 0x0 prop would be 0 inches in diameter and a pitch of 0. therefore it can't exist. If there is something special that I don't know about I will definately stand corrected.