This harmonic balancer is designed for BluePrint Engines small block chevy compatible engines that are externally balanced, meaning the crankshaft itself provides all necessary counterweighting. This size is typical for high-performance street or light race applications. The 6.750" diameter offers a balance between weight and damping performance, helping reduce torsional vibration without excess rotating mass. Comes with mounting hardware and timing pointer. This 6.750 size offers some space saving convenience, as well as less rotating mass vs our standard BPP400 damper. It's functionally identical to the BPP400, with the aforementioned benefits, and even comes with a timing pointer!