Review on BougeRV Waterproof Hitch Cargo Carrier Bag for Car, Truck, SUV, Vans - Ideal for Hitch Mount Cargo Bag, Hitch Trays, and Hitch Baskets (48'' L x 20'' W x 22'' H) by Phillip Samuel

The bag is a good size and holds more than expected. We used this bag to store 4 gym sized gym bags, a large trolley, a swim bag, two backpacks and a few other miscellaneous bags for a family of 6. This freed up a lot of space so our flex wasn't packed. We drove over 2,000 miles round trip in mostly dry weather, but it rained at one of our stops on the way home and everything was dry. Can be a little tricky to close due to heavy plastic construction. It has a Velcro flap that zips up to keep water out. I put it on a roof bag because I liked the idea that it would be more windproof and have less (if any) impact on fuel economy. In the end, we partially unloaded the bag during night stops for safety reasons and put it in the car. We were still able to open the tailgate by pulling it slightly to one side when it was on the Flex. YMMV depends on your vehicle, transport company and how full the bag is.