I got the resistors off Ebay, 3.9 ohm 25 watt ceramic. FYI the fronts aren't air shocks, only the rear. The fronts are electronic damped which is why you need the resistors since the less expensive ones are standard shocks. If you buy the resistors you basically do away with the Z55 designation for the fronts and can buy any shock that fits. The Arnotts have a resistor pack built in which the factory plug connects to which is why they're a bit more than standard but less than factory or Monroe w/ electronic damping.