Rooftop luggage carriers come in soft and hard enclosed forms and as open-topped racks. Companies such as X-Cargo, Thule and Yakima manufacture these carriers. The companies' hard carriers range from 11 to 21 cubic feet in capacity, and their soft cargo bags offer 13 to 16 cubic feet.
While soft cargo bags are cheaper, easier to store when not in use and often don't require cars to have a pre-existing roof rack, they are less durable and often less aerodynamic than their hard counterparts. Hard cargo boxes are better for storing heavy or bulky gear. They are better at resisting the elements and are often easier to load and unload, with larger lids that stay open and in place, according to Outdoor Gear Lab.