Smoke rune

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

In-game examine text: "A combined Air 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 4697.

View on OSRS Wiki

Smoke Rune shows an active flip setup with a margin of +7 gp and 3,699,749 trades over the last 24 hours.

At the buy limit of 18,000 every four hours, max profit per cycle is about 126.0k gp — high margin with healthy liquidity.