The Surly Stainless Steel chainring is made from 304-grade stainless. Stainless is a rust and corrosion-resistant alloy steel that is known for its toughness. Like all things mechanical, it will eventually wear out. When it does, simply flip the chainring around and you’ll get another lifespan out of it. Machine finished to have a 2.1mm tooth thickness and will work fine with 9-speed chains.