Specifically designed and tested over three years to meet the needs of wildland fire crews, these packs ride low on the back like a hip sack but have a fully framed and fully adjustable upper harness. The Mystery Ranch Lightweight Lumbar Wrap locks around your waist and hips to keep the pack from shifting while you work. Polyethylene stiffeners in the sides and bottom of the pack keep the load from sagging onto your butt.