This is for marine grade stainless steel (AISI 316) anti-off bow shackles. Each shackle is laser etched 316. Each shackle comes with a lock ring to keep the shackle from loosening. 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.