Headlight bulbs provide visibility for drivers and alert both pedestrians and other motorists to a vehicle’s presence. Bulbs are primarily composed of glass, a low pressure inert gas, a filament, and wires. Using the electricity provided by a vehicle’s charging system, bulbs produce a strong, steady light. A motorist can alter the bulb’s level of brightness to a low or high beam setting. Motorists tend to use low beams at night or during periods of inclement weather. In contrast, drivers generally use high beams at night when it is especially dark and other sources of lights are unavailable. When bulbs produce light at the high beam setting they can also cause glare, so drivers should be careful when using high beams around others. Some higher quality bulbs will function at optimal levels for several years. All headlight bulbs will eventually require replacement as their filaments fail from use over time.