This 316 Stainless Steel Windlass 5/16" ISO G4 Anchor Chain and is made to "G4" dimensions and complies fully with all requirements of the US National Association of Chain Manufacturers' (NACM) specifications. This is a quality, high grade, marine stainless steel (AISI 316) ISO G4 chain suitable for use in a windlass as anchor chain or other marine applications where high corrosion resistance is desired. This listing is for 20' of windlass chain before the shackles are added. Two quality 3/8" bow shackles are included with the chain. Superb for anchor chain and general heavy duty work in a marine or chemically harsh environment. This chain will fit many standard windlasses. Please consult your windlass manufacturer model manual for the ideal specification for your windlass. The 3 important figures for smooth running or your windlass is the Diameter (DIA), Inside Length (IL) and Outside Width (OW). More details are in the spec table below. This chain is 8.3*26*28.4 (DIA*IL*OW). The measurements of this chain are listed in mm and as G4 is generally considered an Imperial chain, the Imperial spec of this chain is 5/16"*1.02"*1.12". The link size is 5/16" imperial. Every 3 feet links are hallmarked and stamped with 316.