The Rack Sack - Cargo Carrier Bag provides additional car storage when needed and is a great way to free up space in the car for the next big trip. Ideal for camping trips when bringing along a lot of gear, a roof top cargo bag helps keep everything organized.Attach the Rack Sack to your vehicle's roof for your next trip. The large Rack Sack expands your cargo carrying capacity by 13 cubic feet. It is durable and strong by way of the water repellent polyester material. It also features swivel straps that mount to the crossbar or side rails of an existing roof rack, tabs to prevent flapping straps, and a soft felt bottom to protect your vehicle's finish from scratching. Note: For use only with a cargo rack.