Top bag is made of tough, water resistant nylon/polyester pack cloth and fits on top of luggage rack. With velcro straps, it can be quickly mounted on rack or easily lifted off and carried by top strap. The large zippered compartment in center has expandable lid to carry taller items. The 2 zippered pockets have reflective tape and can be expanded to serve as moderately sized panniers for a total volume of 15L. Bottom sleeve contains an elastic water proof rain cover. Top bag can be mounted on rack in combination with side panniers.