Below is a list of light bulb types used in 2012- MERCEDES-BENZ GL-CLASS lighting system, covering SUV vehicles.
Headlight bulb: low beam - H7 or D1S / high beam - H7 or D1S
Parking light bulb: W5W
Brake light bulb: P21W
Back-up light bulb: W16W
Rear fog light bulb: H21W
Boot light bulb: W5W
Entry light bulb: W5W
Reading light bulb: W5W
Light bulb sizes for other MERCEDES-BENZ GL-CLASS generations: GL-CLASS (X164)