Compressed wood wool soaked in wax. They light from a match, burn for around ten minutes, and are the reliable way to get charcoal or damp kindling going.
The reason to specify natural rather than the white paraffin blocks is straightforward: you are cooking on this. Paraffin firelighters smell strongly, that smell transfers to anything cooked in the first twenty minutes, and the usual workaround is waiting, which defeats the point.
They also solve the lighter fluid problem properly. Fluid is a flammable liquid to carry, it flares, and it flavours the food. A firelighter and a chimney starter together light a full load of charcoal in about fifteen minutes with a single match and no accelerant at all.
Keep them in a sealed tub. They are wax and wood and they will take on moisture and lose the will to light in a damp locker, which is the one failure they have.
Worth carrying even if you cook on gas. They are the backup when a canister runs out further from a shop than you planned.