What are Sealed Beam Headlights?
 

I was looking for a kit to convert my xl-style headlights to an xlt style and it says that it is not compatible with sealed beam headlights. What are sealed beam headlights? How do I know if I have them?
(trucks an early 99 f350 xl)

Sealed beams have the bulb built into the headlight housing. When the light goes dead you have to replace the whole thing instead of just the bulb, which is what you do with newer headlights

Cool, thanks for the info!