Spiny helmet

Spiny Helmet is a members-only item on the OSRS Grand Exchange in the armour category.

In-game examine text: "You don't want to wear it inside-out."

It has a Grand Exchange buy limit of 125 every four hours, a high alchemy value of 390 gp, and item ID 4551.

View on OSRS Wiki

Spiny Helmet shows an active flip setup with a margin of +465 gp and 586 trades over the last 24 hours.

At the buy limit of 125 every four hours, max profit per cycle is about 58.1k gp — high margin with healthy liquidity.