This SFI certified damper by Professional Products has many great features- 60 degrees of timing marks, timing marks every 90 degrees, bolt in counter wieghts for externally balance engines, and it looks great too. This damper model can be used without a counterweight for internally balanced engines. Or use one of three supplied counterweights for other engines. This dampers will fit the following applications: a. All internally balanced 318 V8 standard and Magnum, all internally balanced 273 and 340 engines w/forged cranks. No counterweight is used with any of these applications. b. 340 externally balanced 1972-’73 engines w/cast crank. Use supplied 91014 counterweight. c. 360 externally balanced 1993-’97 engines w/cast crank. Use supplied 91013 counterweight. Will not work with '93-'97 5.9L Magnum engine. d. 360 externally balanced 1971-’92 engines w/cast crank. Use supplied 91012 counterweight.