Vapor-tight lights keep dust and moisture out of the fixture, preventing damage to the wiring and components. The housing and lens of these fixtures, also known as gasketed fixtures, fit firmly together and are sealed with a gasket. They provide illumination in areas that are wet, damp, or humid, such as locker rooms, loading docks, public transit shelters, and parking garages. Fixtures with washdown ratings have an IP rating that indicates how well they protect against liquids. To light small areas, round lights accommodate a single bulb. Linear lamps feature a long body that spreads light over a larger area than circular bulbs, providing more coverage. Troffers use drop ceilings to hide their wiring and most of their housing. To cut running expenses, retrofit kits convert existing vapor-tight fixtures to energy-efficient LED technology.