This is the center of the pulley, where it fits around the crankshaft. It has six arms, each roughly 16 millimeters (0.625 inches) long by 1.5 millimeters (0.06 inches) wide at the point where the business end sheared off. It appears to be the thinnest, weakest part of the pulley, by far - a little bit less than one quarter of a square inch of area in total. The aluminum everywhere else on the pulley appears to be many times thicker.