The Ford Flex tail light uses bulb sizes 3157 and 168 and 4157 for the rear lighting system. Data for the lighting components covers the period from 2009 through 2019.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Ford Flex uses two distinct bulb types across its tail light positions: the 168 and the 4157, both of which are ANSI-standard bulbs rated for 12V systems and sold in US and Canadian markets.
The 168 is a miniature wedge bulb in the T10 form factor, rated at 4.9W. It is a single-filament design, making it suitable for low-load indicator or marker functions rather than combined stop and tail duties.
The 4157 is a dual-filament wedge bulb in the T25 form factor, rated at 27W on its high filament and 7W on its low filament. This dual-filament construction allows a single bulb to serve both stop and tail light functions simultaneously.
The inner tail light position on the Ford Flex uses the 168 bulb across the full 2009-2018 model year range, and this fitment is conditional on the vehicle being equipped with halogen capsule headlamps.
The outer tail light position on the Ford Flex (2009-2018) uses the 4157 bulb when the vehicle is equipped with halogen capsule headlamps. This same headlamp condition applies consistently across all ten of those model years.
For the 2019 outer tail light, the specification shifts to the 3157 bulb under the halogen capsule headlamp condition. The 3157 shares the same T25 form factor and 27W/7W dual-filament rating as the 4157, though the two are not the same part number and are not universally interchangeable.
The 4157 and 3157 bulbs share identical wattage ratings and the same T25 wedge base category, yet they carry different ANSI designations. The difference between them typically involves the base indexing or contact configuration, which affects physical fitment in the socket.
For the 2018 outer tail light without the halogen capsule headlamp condition, the specification calls for the 168 bulb rather than the 4157. This represents a different fitment from the halogen capsule variant of the same model year.
For the 2017 outer tail light without the halogen capsule headlamp condition, the specification also calls for the 168 bulb, consistent with the non-halogen capsule 2018 fitment.
The headlamp type on the Ford Flex is a determining factor in tail light bulb selection, as the same model year and position can require different bulb sizes depending on whether halogen capsule headlamps are present.