Pannier Bags are designed to carry heavy loads and normally fit on a rack mounted to the front or rear of the bike, they are usually sold in pairs but single ones are available that will normally fit on either side of the rack. The weight of the load carried should be centred over your wheels, so as to not impair steering or cornering

The Altura range of Cycle Pannier Bags is comprehensive and they mostly feature the reliable klick fix fitting system.The Topeak pannier bags are designed to fit onto Topeak racks but do have straps to fit onto conventional racks.