We will sell this good in set, one set includes 2 bulbs, 2 ballasts, 1 cable and package. Specifications: 1) Power: 35W 2) Voltage: 12V or 24V 3) Efficiency: 95% 4) High lumination: 3,200lm 5) Long life: 10 times longer than ordinary halogen lamps, about 3,000 - 5,000 hours 6) Operating ambient temperature range: -20 ~ +85°C 7) Low voltage protection: when voltage of the battery is less than 9V, ballast will stop working to avoid HID bulb exhausting electric energy 8) Over-voltage protection: when voltage of the battery is more than 16V for trouble of power supply system and battery, ballast will stop working to prevent high voltage from burning bulb 9) Waterproof: up to DIN400500 legal standard 10) Anti-dust: up to SAE J575 legal standard 11) Shockproof: up to DIN40056 legal standard 12) If large quantity , model can be : H1, H3, H3C, H4 (single bulb), H7, H8, H9, H10, H11, 9004 (single bulb) ,9005, 9006, 9007(single bulb), D2S, D2R, D2C