LSX Harmonic Balancer is 30% more efficient above 5,000 rpm and frees up horse power over stock dampers. The shell is CNC-machined and is designed to mount to the crank hub so the timing marks never change position. It features an inertia ring and hub and is rebuild-able and tunable by replacing the elastomer strips. As an added feature, with the exposed inertia weight marked at TDC, you can tell that the elastomer strips need replacing when the marks start to move. All-around, this harmonic balancer has been built to handle your high performance LS engine with ease. Fits LS based GM engines 1997-2012. This product meets SFI Specification 18.1. 6.325" O.D.