What is the 2003 chevy silverado reverse light bulb size?

The 2003 Chevy Silverado uses a 921 bulb for the backup lights. To change the bulb all You will need is a Phillips head screwdriver. Lower the tailgate and remove the two screws that hold the taillight assembly in. One is just above the striker bolt and the other is just below the cable strap. Once the screws are removed, pull the taillight assembly away from the body of the truck takeng, takeng care not to break any of the wiring. From the backside of the assembly rotate the reverse light bulb base, about 1/4 turn to release it from the assembly and pull it out. Pinch the bulb between Your index finger and thumb and pull it straight out of the socket.