These 42mm festoon LED bulbs fit most fixtures with festoon bases in 1-5/8" or 41/42mm. They can replace standard 10W incandescent festoons that are common in courtesy lights and overhead dome fixtures.
 
ILFS42-06W
LED Replacement Bulb, Warm White, 10-30VDC (1.5W), Directional, SV8.5 Socket
 
ILFS42-06R
LED Replacement Bulb, Red, 8-30VDC (1.2W), Directional, SV8.5 Socket