From the manufacturer:

Trekking for a week or more calls for a serious pack. Our plush thermoformed hipbelts and shoulder straps are connected to our sturdy V-stay suspension system to comfortably handle expedition sized loads. This robust pack features WaterTight™ zippers, DWR coated fabrics, and a reinforced bottom to repel the elements.

• Moisture-resistant outer face fabric

• DWR finish (Durable Water Repellent) helps bead water from fabric surface
• Occipital cavity provides unrestricted head movement
• Double-layered fabric pack bottom for added strength and durability

• Interchangeable thermoformed hipbelt
• Interchangeable dual-density shoulder straps
• Thermoformed backpanel

• Removable, quick-release top lid with integrated hip belt doubles as a waist pack

• Six external compression straps