Backpack zephyr 123 line of fully equipped backpacks designed for running mountain bike and light trekking activities the d ns ventilation system ensures perfect ventilation of your back fabric diamond hd carrying system d ns back ergonomic shoulder straps in mesh fabric ergonomic waist band in breathable mesh fabric pockets side pockets in mesh fabric safety pocket front pocket small pocket on waist band collapsible helmet holder accessories extension 3 l which allows to