The bag opens by unzipping to reveal a large bag that provides lots of storage room and then conveniently folds and zips down to easily stow away. The bag is made of 400 Denier nylon. When folded, it measures 13” x 8 ½” x 3 ½” and unfolds to a big measurement of 21” x 12”. Fits on most trunk racks. Features Velcro attachments, zipper closures, deluxe handles, side pockets, shoulder strap and rain cover.