Professional Products 7.25 Inch Damper for Big Block Chrysler features a damper which is supplied as a neutral balance damper with two counterweights with the damper. It features 1972-1978 383 and 400, 1971 383 2-bbl and 1974-1978 440 (cast crank engines only). It uses counterweights 91015. 1970-1971 440 6-bbl and the 1971 high performance 440 use counterweight 91016. All other Chrysler big blocks require no weight. The damper also has two extra TDC marks for either the 426 street or race Hemi. To fit the Hemi, spacer 81013 is also required. This damper will not work on the 331, 354, or 392 early Hemi but basically fits all other big block Chrysler engines including the 351, 361, 383, 400, 413, 426 and 440. Complete instructions are included with the damper.