Hydrobak Hydration Backpack 1.5 L Size:1.5 L this high density Size:5 this high density And with an adjusted rise and a shorter inseam than previous versions or other essentials Helmet Carry: Stow and secure helmet Adjustable Sternum Strap: Offers a range of adjustments for a custom fit and increased stability Reflectivity: For low light safety Light Loop: Clip on a light to make the ride to and from the trailhead safe Tube Trap Management: Keeps your tube secure and accessible when you need it Lightweight and Durable Materials Air Support Light Back Panel: Designed with body mapping technology for efficient ventilation and lightweight comfort Ventilated Harness: Lightweight and breathable Secure Zippered Pocket: Perfect for keys