Ortlieb says about the Atrack
Modular, waterproof travel and outdoor backpack: innovative closure and operating concept with large zip opening on the back: available in three (Atrack) or one (Atrack ST) sizes: Shoulder straps with stepless back adjustment: breathable back support surfaces: padded hip belt: Hip belt pockets: Mesh outer pockets: removable compression straps: Daisy chains on the front: Hermetic opening for drinking tube (drinking system not included): 4 inside pockets: Internal compression: Key hook.
Accessories sold separately: Atrack Hydration System: Attachment Kit for Helmets: Attachment Kit for Gear.
Atrack: back length adjustment 45 liters: XL – M: 35 liters: L-S: 25 liters: L – S.
Atrack ST: specially designed for women: hip fins and shoulder straps adapted to the female anatomy: shorter back carrying system, also suitable for slim men. Back length adjustment 34 liters: M-XS