This is for one (1) quality marine grade stainless steel (AISI 316) spring hook with screw nut and eyelet 1/2". Each spring hook is stamped 316 and laser etched 1/2" with the makers mark. The spring hooks are marked in the US specification style of 1/2". The Metric equivalent is generally considered to be 12mm. Not to be used for overhead lifting. The screw nut adds security so the spring hook remains closed. The eye is removeable. 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.