EXPANDABLE DESIGN: Our bike seat bag features adjustable capacity from 1.5L to 2L through the zipper, so you can easily adjust this it to suit your needs. Dimensions of this bike saddle bag (L x W x H in inches): Before expansion: 9.6 x 4.1 x 4.3; After expansion: 11.4 x 4.1 x 4.3 WEATHER-RESISTANT CONSTRUCTION: This expandable bicycle saddle bag is made with 900D waterproof Oxford fabric and PU coating for enhanced water resistance. PVC-free materials ensure durability without harmful chemicals. *Not recommended for prolonged exposure to heavy rain NIGHT VISIBILITY: Large reflective area around the seat bag to increase night visibility while night cycling. The saddle bag features an additional taillight hook for mounting your taillight (taillight not included in the package) MULTI-COMPARTMENT: The main compartment with built-in mesh pocket provides structured storage for essentials like keys, wallets, cycling gloves, phones, tire repair kits, and accessories. Smart compartment design ensures quick access during rides EASY TO INSTALL: With its strap-on design, this bike saddle bag under seat allows for customizable positioning under any seat, fitting a broad spectrum of bikes, from electric to traditional. Its adjustable Velcro straps ensure a secure and snug fit across various bicycle models, offering a stable and convenient storage solution for cyclists