Repeat damper removal and installation can reduce vibration control. Maintain recommended Fluidampr press fit of 0.0005 0.0015. Fits Fluidampr #800151 and #80256E. Chevy 396-427ci, internal balance, dual key (1/4 and 1/4).Harmonic Balancer Adapter Hub Fluidampr BBC Internal Balance Dual Key, 1/4, 1/4 EachFits Fluidampr #800151 and #80256EHub only