No ordinary bag, this. Yes, it's a bit on the expensive side, but the baby of Frost River's Isle Royale family is crafted from waxed cotton canvas, leather and brass by master craftsmen in Duluth, Minnesota - and it comes with a lifetime guarantee. Great for carrying around that spare bottle of oil, then.
The backpack features a double canvas base for added protection and has two rear pockets, plus an axe sleeve and map pocket. Its compacted volume is about 18 litres and it expands to 33 litres. Great for catching all that leaking engine oil, too.