Roof top storage system. The outer material is a combination of soft neoprene material to protect your paint and durable nylon for long life. Each Auto Backpack features four tie down points to make installation easy and secure. Designed to provide quick alternative storage, these easy to use and store roof top storage bags are a must for those road trips. With 20 cubic feet of storage space, this is a perfect alternative to those expensive and hard to store plastic pods.