Since PVC plastics harm not only our environment but also our health, Ortlieb offers the Back-Roller Classic models with a PVC-free construction. The Back-Roller Free Panniers are a splitting image of the classic variation with an exception of the PVC. Their rugged canvas material has a polyurethane coating that sheds water spray, dust, and abrasion, and the roll-top design continues to block raindrops from dampening your bike touring gear. Apart from that, the Classic and Free are more or less the same. The QL2. 1 system lets you mount and release each pannier with a simple pull of a handle. The pannier automatically locks onto the rack the moment you mount it; it's compatible with 16mm racks, but Ortlieb includes hook inserts to fit 8, 10, and 12mm racks as well. The QL2. 1 system also features a semi-elliptical hook at the bottom that you can adjust and rotate to fit your rack so the pannier doesn't bounce as much as regular panniers.