JEGS SFI Diesel Harmonic Balancers are manufactured using a unique process which heat bonds, under extreme pressure, the dampening isolator to the center hub and the inertia ring. This process is proven to eliminate slippage and separation of the hub & inertia ring. The hub and inertia ring are made from forged steel and have timing marks every 90 degrees. The black finish provides good looks and added strength and durability. SFI 18.1 approved for race use. Shipped in a heavy duty wooden box.