When I first bought the car 2 years ago, there is no bulb inside this car internal reading light casing. I thought they were faulty, but no hard trying. I bought a some Festoon LEDs for it, initially they were too short (32mm and 34mm), and finally I got the 39mm size for it, which is perfect.
Earlier time I can only find white LED type, but later I found this yellow LED type, which I much preferred. This festoon yellow LED type is also not as warm as the white LED type that I have bought previously.
Cost? Only RM1.58 a piece (US$0.35).