Replacement for the original \’S\’ big end nut, this looks the same but is an up to date modern nut that grips on the thread replacing the plastic nyloc type. The original plastic insert type, when under stress from very hot engines became liable to disintegrate. Alternative nut EAC5541A is a multipoint nut from the later series of nuts with a clamping shoulder base. Sold singly, 8 required per engine.