These 3-7/16" standard bore, standard compression stroker pistons are part of an S&S stock bore stroker kit for 1936-'84 HD® big twins, and are designed to be used in conjunction with S&S® stroker flywheels. Flywheels of the following strokes may be used for the following displacements: 4-1/2" stroke - 84" @ 8.4:1 compression, 4-5/8" stroke - 86" @ 9.4:1 compression, 4-3/4" stroke - 88" @10.8:1 compression.