Osram 54817 HPL ULTRA PLUS (UCF) are an improved product line of the HPL family of lamps designed specifically for the Source Four series of fixtures. The HPL Ultra Plus uses Osram's Ultra Compact Filament (UCF) design for maximum efficiency and life. The unique top bridgeless construction virtually eliminates filament shadowing, allowing for crisper images than ever before. HPL Ultra Plus (UCF) brings increased opportunities for all stage, studio, TV, and architectural applications with superior light performance and maximum efficacy.