These Professional Products SFI Spec PowerForce Plus dampers provide more applications for a wider range of engines. All Professional Products PowerForce Plus dampers feature a bonding process, which adheres the elastomer to the i.d. of the inertia ring and the o.d. of the hub. Through subsequent research and development, Professional Products has perfected a new process that utilizes a stronger adhesive, along with an improved elastomer, to create a much stronger bond. Professional Products dampers all feature clear, white, easy-to-read timing marks against a painted black background. In addition, they engrave a mark every 90 degrees, which is also painted white (90 degree marks are not on small block Ford dampers). You won't find any dampers that are more accurately balanced or more closely machined for the correct fit than the Powerforce or Powerforce Plus line of high performance street or SFI Spec racing harmonic dampers.