A rod that throws very hot sparks when scraped - works when wet and lasts thousands of strikes.
Look for
A rod at least about 3 inches long and 3/8 inch thick for an easy grip
A striker with a sharp, square edge
A lanyard so the rod and striker stay together
Avoid
Very thin "keychain" rods as your only fire starter
Tip
Practise at home (safely) before you need it - technique matters more than the rod.
This guide is general advice and will be checked by a preparedness reviewer before release. Partner reviews and store links will appear here later, always clearly labelled.