Primary gear thrust washers are made in varying sizes to take up the play.Standard gap size should be between 3-6 thou. This type is for the 1275cc crankshaft only which has a raised step for the primary gear to sit on. Race applications can be increased plus 3 thou. Thrust washer 0.120-122”(3.04-3.09mm). The measurement is taken as plus or minus one to the size hence the two thou tolerance on each part numbe.