20Twenty Lighting Festoon 42mm 3SMD LED BulbFestoon Bulbs replace interior lights in vehicles, replace any 12Volt bulb in vehicles including, Truck Cargo light, Dome light, map light, interior door light, glove box light. Our Festoon bulbs have CanBus built into the light meaning, they are designed to work with vehicles that have a CanBus system (means they are built in resistors or decoders) that prevent issues such as Flickering & Error messages. Bulb sizes vary for each vehicle.