The Flex Capacitor features a unique patent pending gusset system that allows the pack to quickly and easily expand from 40-60 liters with the adjustment of a few straps. Instead of expanding up like other packs, the circumference of flex expands to provide a more stable and comfortable load carry. Features: - Lightweight "Y-FLEX" suspension - EVA foam hip belt and shoulder straps - Raised lumbar and scapula pads (EVA foam) - Load lifter straps - Hip belt stabilizer straps - Adjustable hip belt - Expandable 40-60L volume (volume varies between sizes) - Ultralight weight design - 2 torso sizes (non-adjustable) - 4 hip belt sizes - U-shaped top access zipper - Zippered stash pocket on lid - Removable reservoir sleeve - Shoulder strap water bottle pocket - Stretch mesh side water bottle pockets - Two hip belt pockets - Compression straps - Ice axe/trekking pole loop - Body Fabric: 100D Nylon-Poly Ripstop - Secondary Fabric: 420D Nylon Oxford - Stay Material: DAC Pressfit Aluminum - Number of Stays: 1 "Y-FLEX" stay