This is a quality marine grade stainless steel (AISI 316) G4 1/4" x 4' Windlass chain specifically cut for anchor chain. The link size is 1/4". Included are two marine grade stainless steel (AISI 316) anchor shackles. Each shackle is 5/16". The total length of chain is 4' measured before the shackles are added. The chain link are in the US style of 1/4" (for the chain link size) and 5/16" (for the shackle size). The metric equivalent of the shackle is generally considered to be 8mm. This chain is made in the USA and assembled in the USA with some imported components. 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.