The L stands for "low power" compared to the other high power bulbs. We like to call these the "Regular Power" halogen bulbs becuase they equal the wattage power consumption of your factory bulbs. Over time headlight bulbs dim, long before they burn out. Vision X provides three lines of headlight replacement bulbs to best suit your needs. Our bulbs are superwhite, not the standard orangy-yellow color, for a more natural light color that increases visibility, provides for better depth perception, and reduces eye fatigue.