The Lumileds Philips MasterDuty Headlight Bulbs are designed to handle rough terrain and damaged roadways while providing protection against mechanical shock for medium and heavy duty Class 2 through 8 truck applications. The headlight bulbs have a run-time of up to 550 hours and are able to withstand a wide range of vibration frequencies. They are built with a high-performance glass that withstands temperature and pressure changes.