Mooring chain Introduction: Depending on the nominal tensile strength of the steels used for manufacture, chains are to be subdivided into five grades, i.e.: R3, R3S, R4, R4S, and R5. Diameter:34mm-162mm Grade: R3, R3S, R4, R4S, R5 ABS, LR, BV, DNV, CCS Certificate Applications: offshore oil platform, offshore oil storage ship, offshore buoys, fishing farm, and aquaculture purposes.