New radiator cap with sacrificial anode. Choose from 13# or 16# cap. Will fit datsun 240Z, 260Z, 280Z, 280ZX and 510. This is a patented, scientifically tested radiator cap with a magnesium sacrificial anode attached to the bottom of the radiator cap that hangs down into the coolant. The anode is designed to attract and absorb the electrical energy that causes electrolysis and the magnesium is consumed instead of the aluminum components in the cooling system, thereby reducing repair and maintenance costs.