CSR Flexplates are designed to withstand the stresses of today's high horsepower engines--especially those with nitrous oxide and high stall converters. This Aluminum Core plate with Steel Bolt on Ring Gear is the epitome of lightweight strength, coming in at just 5.8 lbs. Fits all 2 piece rear main seal, 168 Tooth, Internally Balanced, on Chevrolet Big Block. Exceeds SFI specification 29.1. Certification is valid for 3 years.