This is a Ushio 500 watt BTL bulb. It has a base of P28s medium prefocus which is in Industrial Light and Specialty Lamps. It has a color temperature is 3050k, it has a filament of C-13D, and it has lumens of 11000. This Ushio 500 watt BTL has a maximum overall length of 4.953 inches, a rated life of 500 hours and a shape of T6.Cross Reference:Atlas/Thorn HX17 Atlas/Thorn T/17 Bulbrite 762010 BTL Colortran 176-167 GE 11966 BTL-Q500T6/CL/P Grainger 6VN47 Osram Sylvania 54685 BTL 120V Philips 31891-5 BTL 500W 120V Philips 6800C Sunlite 70005 BTL Ushio 1000083 BTL, JCS120V-500WBBaseP28s Medium PrefocusBulb TypeHalogen BulbsColor Temperature (K)3050KDiameter (in) 0.7677FilamentC-13DLuminous Flux (LM)11000 Maximum Overall Length (in) 4.953 Rated Life (Hours)500ShapeT6Voltage (V)120VWattage (W)500W