50 Watt M110 Quad Tap Metal Halide Ballast KitMetal Halide Ballast Cross Reference: Keystone Metal Halide Ballast Advance Ballast 71A5191 Universal M50MLTLC3M GE GEM50MLTLC3D 5 Venture V90D5731K High Intensity Discharge (HID) lamps require a ballast to apply starting voltage to the lamp and establish current flow an arc between the lamp electrodes. Without a ballast, the arc will extinguish or draw increasing current until some circuit element burns up. Ballasts provide system stability by