We ordered a clutch kit from Spec clutches that included a throwout bearing, pilot bearing, flywheel, pressure plate, clutch disc, and new flywheel, and new pressure plate hardware. We noticed the clutch assembly arrived bolted to the new flywheel, which we had never seen before. Dave Dibs at Orange County Transmissions pointed out that the assembly was balanced. He says on average one out of five clutches that he sees are about 8 grams out of balance and that causes first-order vibrations. He suggests balancing clutches to flywheels for everything he works on, even Jeeps.