This is for two (2) quality marine grade stainless steel (AISI 316) wire rope thimble casting with closed end made specifically for casting applications. Each thimble is made of casting material and has a closed end. The thimble has strong, robust and thick side walls. Each thimble is stamped 316 and marked in the imperial style of 1/4", as well as M6 for metric. For wire rope size of 1/4". The metric equivalent is generally considered to be 6mm. 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.