The Double Back Option is fairly simple – basically you are betting that your score will be in the top half of the shooters scores participating in the option.
If your score happens to be at the exact mid-point, then all shooters with that score will split the payout. As an example, the entry fee for the option is $10. Shooters with scores in the top half will be paid $20 and the shooters with scores in the bottom half will receive $0