Steam rune

Steam Rune is a members-only item on the OSRS Grand Exchange in the runes category.

In-game examine text: "A combined Water and Fire Rune."

It has a Grand Exchange buy limit of 18,000 every four hours, a high alchemy value of 12 gp, and item ID 4694.

View on OSRS Wiki

Steam Rune shows an active flip setup with a margin of +2 gp and 2,995,537 trades over the last 24 hours.

At the buy limit of 18,000 every four hours, max profit per cycle is about 36.0k gp — high margin with healthy liquidity.