High Pressure Sodium HID Bulb, ED18 Bulb Shape, Mogul Screw (E39) Bulb Base Type, High Pressure Sodium, 28, 500 lm, Bulb Operating Position Universal Burning, 250 W, Trade Number C250S50/ALTO, Rated Life 24, 000 hr, Standard Bulb Type, 2, 100 K, 360 Degrees Bulb Beam Angle, 2 1/4 in Bulb Dia., 9 3/4 in Overall Length, Shatter-Resistant No, Bulb Finish Clear, Color Rendering Index 21, Bulb Minimum Starting Temperature -40 Degrees F