Below is a list of light bulb types used in 2006-2012 MERCEDES-BENZ GL-CLASS lighting system, covering SUV vehicles.
Headlight bulb: low beam - H7, D1S or D2S / high beam - H7
Parking light bulb: W5W
Fog light bulb: H11
Front indicator/turn signal bulb: PY21W or WY5W
Rear indicator/turn signal bulb: PY21W
Tail light bulb: P21W
Brake light bulb: P21W
Back-up light bulb: P21W
Rear fog light bulb: H21W or P21W
License plate light bulb: C5W
Interior light bulb: W5W
Door light bulb: C5W
Boot light bulb: W5W
Reading light bulb: W5W
Light bulb sizes for other MERCEDES-BENZ GL-CLASS generations: GL-CLASS (GLS/X166)