This 316 Stainless Steel Windlass 1/4" 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 5/16" 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 7*21.5*24.4 (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 1/4"*0.84"*0.96". The link size is 1/4" imperial. Every 3 feet links are hallmarked and stamped with 316.