Premium Halogen Globes are manufactured of both quartz and hard glass.  UV additives are added to the quartz globes to ensure they are safe for use with polycarbonate headlamps whilst hard glass globes are UV cut.  All globes are pre-focused and most are manufactured to the specific criteria of the European "E" standard (ECE R37/ADR 51/00).  The light colour of halogen globes is measured in degrees Kelvin, the rating for standard halogen globes being 3200°K.