M-Class basic carrier

Both Thule (pronounced "Too-Lee") and Yakima racks will work on the ML, and plenty others too, but those are two names I looked at for my ML430. The application listings for each of those manufacturers lists virtually every car and sport utility vehicle made, so it'll be easy to avoid a dealer.

You'll need two components: The (4) base clamps that go onto the ML roof rails, and the (2) crossbars that fit across the roof into the base clamps. From there, you can add a rooftop cargo carrier, ski rack, bike rack, skiboard/wakeboard rack. Basic system would be about $200-$300 for the base clamps and crossbars.

Both systems are available at REI, but any place that has roof rack systems will have one that will fit an ML.