The high-quality, low-profile design features an included 1.5-liter reservoir that slides into its own exterior pocket with a bite valve that attaches magnetically to a sternum strap. A well-ventilated mesh harness offers exceptional airflow and rolled, soft-edge shoulders provide contoured comfort and stability. In the event you find yourself outside when the sun goes down, a loop for your rear tail light lets you be seen. Made with mountain bikers in mind, but practical for any activity where hydration is a must.