GPH450T5L/4 Ultraviolet Sterilizer Bulb
GPH450T5L/4
Type: 17 3/4" Germicidal Lamp
Connection: 4 pin one end
This bulb might not necessarily be manufactured by your utraviolet system's manufacturer, but it functions correctly as a replacement for this system.
Manufacturers recommend changing your UV Sterilizer Bulb once a year.