The main compartment of a bicycle trunk bag with a maximum capacity of 10 liters can help organize small items. There are pockets on each side, which can expand the capacity to accommodate many small objects and sundries. It can also be used as a messenger bag. The drawstring design of the bottle cage helps prevent the water bottle from falling during bumps. The strap on the back is used to connect the taillights. If you are a night rider, you need to add some reflective items to ensure your safety, it is firmly fixed to the rack and will not move.