This is for two (2) quality marine grade stainless steel (AISI 316) 16mm thimbles. Each thimble is lasered 316 and the metric size of 16mm. For wire rope size of 5/8". 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.