Ushio brand MR16 halogen special purpose lamp. ANSI EJV. 150 Watts for more power and light. 21 volts for specialty low voltage systems. Low voltage means a smaller fillament, for greater optical control.
NOTE - this is not a general purpose lamp. Light output is greater and color is brighter than equivalent halogen lamps, but rated life is only 40 hours. Generally used in dental photo curing applications.
NO LENS - enclosed fixture recommended