Description: Lightweight and Foldable Design: This outdoor sports backpack is made of lightweight polyester materials, making it easy to carry without adding extra burden to cyclist. It also features a foldable design that can be easily folded into a compact size when not in use, saving space in your home or bike basket.Double Shoulder Backpack Design: The double shoulder backpack design effectively disperses weight, reducing pressure on the shoulders during long periods of wear and enhancing comfort during cycling. This versatile backpack is not only suitable for cycling but also for daily commuting and short trips, offering high practicality.Built in Helmet Net: The cycling backpack built in helmet net allows cyclists to quickly store their helmets, preventing them from shaking or getting lost during cycling. The helmet net also helps keep the interior of the backpack tidy and organized, improving overall user experience.Hydration Bladder Compartment/Hydration Bladder Clip: The built in hydration bladder compartment or clip allows cyclists to carry a hydration bladder conveniently anytime and anywhere during cycling. The hydration bladder clip ensures stability of the bladder during cycling, preventing it from shaking or leaking.Proper Size: The running backpack with reflective stripe is in size 45cmx22cm/17.72inchx8.66inch, for both men and women, suitable for various outdoor activities, like camping, hiking backpacking, fishing, climbing, biking, etc. Specification: Material: Polyester Size Chart: 45cmx22cm/17.72inchx8.66inch Package Includes: 1 Hydration Backpack Note: Please allow slightly errors 1-2cm differences due to manual measurement.