This is for ten (10) quality marine grade stainless steel (AISI 316) Rectangle Adjusting Rings 5mm x 20mm (3/16" x 3/4"). Each Rectangle Ring is stamped 316. 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.