The ROCKBROS Bike Rear Rack Bag is a waterproof, multifunctional trunk bag designed for serious cyclists who need dependable on-bike storage and versatile off-bike use. Built for commuters and weekend explorers alike, it pairs rugged durability with smart organization.

• Waterproof, Durable Materials: Crafted from nylon, microfiber, and EVA with a carbon composite leather exterior to resist rain and wear, keeping contents dry ride after ride.
• Expandable Storage to 35L: Side compartments unzip to transform the bag from a compact 17L capacity to a full 35L pannier, perfect for groceries, gear, or long trips.
• Multifunctional Off-Bike Use: Comes with two detachable shoulder straps, so you can convert it into a messenger or shoulder bag for commuting or weekend adventures.
• Padded, Shock-Absorbing Interior: Cushioned compartments reduce impact and protect valuables, with a removable divider for flexible organization.
• Rigid, Integrated Hard-Shell Structure: A built-in frame keeps the bag’s shape and shields items from deformation during rides or when parked.
• Secure Attachment & Night Visibility: Stable mounting on your rear rack plus reflective elements enhance safety in low light.
• Practical Capacity & Lightweight Design: Before expansion about 17L, after expansion up to 35L; weighs around 1086 g, with five interior compartments.

With its weatherproof build and expandable capacity, this ROCKBROS bag handles daily commutes and weekend trips with equal ease. The combination of a rigid shell, padded interior, and organized compartments protects clothes, electronics, cameras, and tools from moisture, impact, and misplacement. Off the bike, easily sling it as a messenger bag to carry your essentials, then snap it back onto the rack for your next ride. The reflective details and reliable attachment system offer peace of mind for night cycling and busy urban streets.