This is a standard size 35 Watt (35W ± 0.5W) HID Ballast from Lumens. These are sold in singles (Price is PER ballast)
Digital ballasts also converts DC power from vehicles to AC power, but also have added DSP chips to improve the stability of power used to power the HID bulb. With a smaller fluctuation in power, the HID bulbs will reach their potential lifespan.
All Lumens products have 90 days of warranty.