This is a great reproduction of the pulley GM used on the 396 - 375HP BBC engines in Chevelles, Camaro's AND SMALL BLOCK 302'S IN THE Z-28. It measures just under 3 5/8 inches in diameter. The OEM part # it replaces is 1970831. Another accuratly plated and correct O.E.M. replacement for 68 – 70 Hi Perf 396 engines in Camaro and Chevelles, and also Z-28 Small Blocks