ATI ZL1 / LSA Super Damper - 918859 - Dual keyway

the ATI #918859  balancer for use with 8/10/12 Rib supercharger pulleys (Supercharger Pulley NOT Included, Rear AC Pulley NOT Included) Belt Spacing: Corvette/LSA/ZL1 Engine Balance: Internal Safety Rating: SFI 18.1 Degree Markings: Yes Degree Marking Range: 360 Outside Diameter (in): 7.480 in. Harmonic Balancer Material: Aluminum/Steel Harmonic Balancer Construction: Elastomer Harmonic Balancer Finish: Black anodized Mounting Hardware Included: Yes Rear AC Pulley: NO Are you looking for maximum engine protection and performance for your serpentine belt application? ATI Super Damper serpentine harmonic balancer's contain grooves for serpentine belts machined into the outer damper shell. The dampers come standard with six outer grooves for standard OEM drive systems. Specifically designed for high-rpm engines, they're tuned to eliminate the harmful crankshaft harmonics that cause parasitic horsepower loss. These balancer's are tunable in the field, rebuild-able, and e