What type of bulb does an F150 rear turn signal use?

It is a combination turn and brake light, with a double contact on the bottom of the bulb. Go to a Ford dealer and take the bulb out and go in and ask for a new one, and get a spare bulb for next time, too. Install the new bulb and replace the lenses carefully, as the plastic can be broken if you tighten the screws too much. Make sure you get the waterprofing gasket in properly, or the tail light assembly will fill with water when you wash the truck next.