Rear chain joiner / con link (connecting link), 520, 5/8 x 1/4 in, Renolds Synergy. The original rear chain fitted to Nortons 1928 to 1945; 1946/7;1949/51; 1952/53; 1954/56. Use any other chain on a Norton and risk wearing away the primary case, chain guard and gearbox shell.. Renold Synergy chain lasts up to 6 times the life of other brands see Renold synergy website10B-1RN S NA Cl 26 GY10BINAS26I