Ironwood plank

Ironwood Plank is a members-only item on the OSRS Grand Exchange in the bars category.

In-game examine text: "A plank of robust ironwood."

It has a Grand Exchange buy limit of 13,000 every four hours, a high alchemy value of 900 gp, and item ID 31435.

View on OSRS Wiki

Ironwood Plank shows an active flip setup with a margin of +83 gp and 83,806 trades over the last 24 hours.

At the buy limit of 13,000 every four hours, max profit per cycle is about 1.08m gp — high margin with healthy liquidity.