Collection: C5W / C10W Bulbs

The C5W bulb: electric reference for the festoon bulb

The C5W is the CEE electrical designation for the festoon dome light bulb:

• C = Festoon base (festoon in English = cylindrical at both ends)
• 5 = 5 watts of power
• W = tungsten filament

The C10W is the 10W version for larger dome lights (rare but existing).

C5W = Festoon = SV8.5

Three nomenclatures for the same family of bulbs:

• C5W — electrical designation (this page)
• Festoon — French commercial name for its shape
• SV8.5 — technical designation of the base (8.5 mm contact)

These designations are strictly equivalent — you can buy under either name interchangeably.

The 3 C5W lengths: 31, 36, 42 mm

Criterion No. 1 for the right choice — the total length of the festoon bulb must match the housing:

• C5W 31 mm — small dome lights, city cars (Clio, 208, C3, Aygo, etc.)
• C5W 36 mm — most common standard size (Mégane, 308, Golf, and most sedans)
• C5W 42 mm — large dome lights, minivans, SUVs, some voluminous trunks

To measure: remove the old festoon bulb and measure its length from contact to contact with a ruler. The size is sometimes also indicated in the vehicle manual or on the original bulb packaging.

Uses of the C5W

• Main dome light (front and rear depending on the vehicle)
• Trunk lighting
• Courtesy reading lights (map lights integrated into the headliner)
• Door sill lighting on some vehicles
• Glove compartment lighting and compartments

C5W LED: immediate cabin transformation

The switch to LED is one of the most cost-effective modifications in terms of visual rendering:

• Pure white light (vs halogen yellow) — instantly modernizes the interior look
• Almost unlimited lifespan — no more replacements
• Customizable colors (cool white, warm white, red, blue...) — no legal restrictions for interior use
• Compatible with most vehicles without special canbus