Festoon LED Bulbs - 31mm/36mm/39mm/41mm

What Is a Festoon Bulb?

A festoon bulb is a tube-shaped bulb with metal contacts at both ends. In cars, festoon bulbs are commonly used for car interior lights such as dome, map, trunk, cargo and courtesy lights, as well as some license plate lights.

Festoon LED bulbs replace compatible factory incandescent or halogen bulbs while using less power. The correct replacement depends on the bulb length, original bulb number and vehicle application.

For more details about sizes, uses and replacement types, see our festoon bulb guide.

Festoon Bulb Sizes: 31mm, 36mm, 39mm & 41mm

Festoon bulb sizes are usually identified by their total length in millimeters. SEALIGHT currently offers four common sizes:

A festoon bulb size chart helps narrow down the right replacement, but reference numbers are not always universal across manufacturers. Some aftermarket bulbs with the same reference number may be listed at slightly different lengths.

For example, some 578 or 211-2 replacement bulbs may be sold as 41mm or 42mm. Compare the actual bulb length and original bulb number before buying.

How Do I Measure a Festoon Bulb?

Measure the full bulb from the outside of one metal end cap to the outside of the other. Use millimeters when comparing it with a 31mm, 36mm, 39mm or 41mm festoon bulb.

Also check the number printed on the original bulb and its lighting position. A dome light, trunk light and license plate light on the same vehicle may use different bulb sizes.

Do not choose a replacement by length alone. Confirm the bulb number and lighting position, then use the Automotive Bulb Finder to check vehicle fitment. Do not bend the contacts, modify the socket or force a bulb into a housing if the size does not match.

Festoon Bulb vs. Wedge Bulb: What’s the Difference?

A festoon bulb has metal contacts at both ends and clips between two contacts. It is usually selected by its length.

A wedge bulb has one plug-in base. Common automotive wedge bulbs include T10/194/168 LED bulbs. Both bulb styles can be used for vehicle interior lighting, but their sockets are different. They are not interchangeable unless the housing is designed for that bulb type.

Why Choose SEALIGHT Festoon LED Bulbs?

• More Size Options: Choose from 31mm, 36mm, 39mm and 41mm festoon LED bulbs for different compatible applications.

• Crisp 6500K White Light: A clean white upgrade for compatible dome, map, trunk, cargo, courtesy and license plate lights.

• Compact 1:1 Design: Made to fit compatible factory festoon housings without changing the original socket.

• IP67 Protection: Built to resist water and dust for dependable use in compatible interior and exterior light positions.

• Fitment Support: Use the SEALIGHT bulb finder or contact customer support if you are unsure about bulb size, application or LED compatibility.

• Easy Purchase Protection: Enjoy free U.S. shipping, 90-day returns and a 1-year warranty on eligible products.