Shimano Unzen Bike Hydration Backpack Black/Lightning Blue, 2L Helmet Holder:This versatile clip allows you to securely attach your helmet to the bag. Eyewear Holder: When you take off your eyewear, you can hang it in this dedicated holder. Hydration:Hydration compatible bag is equipped with a dedicated section for securely holding the included hydration system. Reservoir Compression:This function helps improve stability by stopping water from sloshing about when levels run low in the hydration pack. Light Attachment Loop:A rear-mounting light-attachment loop works in tandem with reflective elements to provide peace of mind when you find yourself caught in traffic after dusk.