The barrel pack and harness is ubiquitous with canoe tripping. We use ours for packing our food- although not 'bear-proof' per se, it certainly does keep the racoons and mice munching on pine cones through the night. These barrels will help keep your stuff dry during the occasional dunking in the water. We also find the barrels double well as a stool when sitting around the fire or picnic table.
The 30L barrel is a good size for two people on trips 1-3 nights, or a larger party for a single night. It fits well vertically behind the stern seat in most canoes.
The 60L barrel is great for longer trips and especially well for longer trips with larger groups. This monster fits perfectly between the gunwales of our canoes. Keep in mind, 60L of food can get extremely heavy...