What size ferro rod is best for beginners?

Specialist community consensus points to a 1/2-inch-thick rod in the 5–6 inch range as the sweet spot. Thicker rods throw bigger spark showers and are easier to grip with cold or gloved hands, and the length gives you many more strikes before the rod wears down. Thin 1/4-inch keychain rods work but are fussier and wear out faster.