This listing is for a OE-Replacement balancer (damper) and bolt compatible with Chevrolet GEN I small block V-8 engines requiring an internally (neutral) balanced 6.12" OD balancer. Engine Balance: Internal Safety rating: Not SFI approved degree markings: Yes, Outside diameter: 6.120", Material: Nodular iron, Construction: Elastomer, Black painted, Crank Bore: 1.24", Nose diameter: 1.76" Weight: 4.63 lbs., Overall width: 2.34".