Mercedes-Benz C350 Dome Light Bulb Size

Additional Notes

• The Mercedes-Benz C350 dome light uses two distinct bulb types across the 2006-2015 model years: the 6411 and the 12961.
• The 6411 is an ANSI-standardized bulb designation recognized across the United States and Canada, while 12961 is a Philips part number referencing a miniature wedge bulb of the T10 family.
• Despite their different physical forms, both the 6411 and the 12961 operate at 12 volts and 5 watts, meaning they share identical electrical ratings.
• The 6411 is a festoon-style bulb measuring 36mm in length with an SV8.5 base, a cylindrical form factor that seats by pressing between two spring-loaded metal contacts at each end of the housing.
• The 12961 is a miniature wedge bulb using a W2.1x9.5d base, a baseless design where the glass envelope itself is pinched and inserted directly into a wedge socket.
• Because the 6411 and 12961 use fundamentally different base types, festoon and wedge sockets are physically incompatible, and the two bulbs are not interchangeable with each other.
• The Mercedes-Benz C350 (2006-2007 and 2011-2015) takes the 6411 festoon bulb for the dome light position.
• The 2008-2010 model years require the 12961 wedge bulb instead, indicating a different dome light socket assembly was used during that production period.
• The SV8.5 base designation on the 6411 refers to a festoon cap with an 8.5mm contact cap width, a standard measurement used to ensure proper fitment within the spring-clip housing.
• The W2.1x9.5d base designation on the 12961 specifies a wedge base 2.1mm wide at its narrowest point with a 9.5mm pin spread, defining the exact socket geometry required for that bulb.