575W/120V, tungsten halogen, HPL series, Ultra Compact Filament (UCF) "HPL lamps" are a group of stage & studio and architectural lamps and have been specifically engineered to work with ETC Source Four fixtures. Though HPL lamps are available in various wattages and voltages they all feature G 9.5 medium 2-pin bases with heat sinks. OSRAM 54817 is a "HPL 575" that runs on 120V and is a member of OSRAM's UCF (ultra compact filament series. UCF lamps feature compact filament design that improves light collection, light output, and efficiency.