IDEAL CAPACITY: 0.75 liter capacity, good for holding daily essentials. Bike Bag under seat is roomy for gas cylinder, tube, tools and miscellanea, small wallet and/or keys. If there need a little extra space it has an expansion zipper which will add a decent amount of space.STRAP-ON DESIGN: Upgraded stylish design bike saddle bag. Concise style, better material, better size. Fixed securely with 2 strap, the straps fit securely and neatly under your saddle and around the seat post which suits for the most road, mountain and commute bikes.REFLECTIVE DESIGN: The both sides of this water - repellent saddle bag have reflective logos to increase night visibility in low light or dark conditions. It has a loop on the back which allows you to clip on a bike light. ( Tips:Taillight doesn't include in the package )EASY ATTACH ON & REMOVE: This saddle bag is the wonderful size, aero and has two strap that wrap around your aero seat post. And it can hugs the seat very tightly up an out out the way. It is easier to take the bag off of the bike and then re-attach it when needed.INNER COMPARTMENTS: Convenient for you to separate bike tools, keys or somethings which need to. The bike seat bag will hold the basic needs of the ride.