A box of solid fuel cubes that light easily and burn for several minutes each.

The hard part of a fire in bad conditions is not the spark, it is the first five minutes. Wet kindling needs sustained heat to dry out and catch, and a fistful of dry grass does not give you that.

A fuel cube burns long and hot enough to do it, so one cube turns damp wood into a fire instead of a frustrating hour.

They light from a match, a lighter or a ferro rod, and they are unaffected by being rained on in the packet.

The thing most fire kits are missing.