1. Large Capacity: With a capacity of 30 liters, this backpack allows you to carry carry-on luggage and spare items without added shoulder strain. It reduces pressure on your shoulders and meets the needs of long-distance travel. 2. Waterproof: Made from high-quality waterproof nylon fabric, it resists water penetration during rain. Designed with durable, tear-resistant material and reflective logos to enhance visibility and safety during outdoor use. Effectively protects your belongings. 3. Ergonomic Design: The trapezoidal shape prevents heel contact with the backpack while riding. Features secure buckles on the front, back, and sides of the bike seat bag for stable and firm attachment. 4. Multifunctional Storage: Main compartment includes a double zipper for easy access and secure closure. Includes four expansion pockets and two mesh side pockets for organizing frequently used items. Rear reflective reflector improves visibility and safety during night rides. 5. Wide Compatibility: Fits most bicycles with rear seats, including mountain bikes, road bikes, and e-bikes. Also compatible with various bike frames. Ideal for long-distance cyclists.