This is for marine grade stainless steel (AISI 316) bow shackle. Each shackle is stamped 316 and laser etched in imperial specification with the manufacturer's mark. Not to be used for overhead lifting. AISI 316 stainless is a premium grade of stainless and is considered by many to be best in class. 316 stainless is corrosion resistant and very durable even in the harshest of conditions.