Fully featured expandable trunk bag with expanding main compartment and drop down sides that take it from 9L (550 c.i.) to 36L (2197 c.i.) of capacity Customer requested additions such as adjustable dividers, ice pack compartment and elastic cords for taking extra layers for unpredictable weather Mesh helmet holder on the exterior keeps your helmet safe and secure during stops for provisions Waterproof design and polyester materials keep your gear dry should you run into inclement weather Equipped with Basil`s Universal UBS system and compatible with all rack types