Iron bar

Iron Bar is a free-to-play item on the OSRS Grand Exchange in the bars category.

In-game examine text: "It's a bar of iron."

It has a Grand Exchange buy limit of 10,000 every four hours, a high alchemy value of 16 gp, and item ID 2351.

View on OSRS Wiki

Iron Bar shows an active flip setup with a margin of +2 gp and 832,182 trades over the last 24 hours.

At the buy limit of 10,000 every four hours, max profit per cycle is about 20.0k gp — high margin with healthy liquidity.