CNC Machined from aircraft grade 7075 T-651 Aluminum and have been tested to an average of 12,500 rpm ARC Billet Rod Stroker Enduro * The Enduro line of ARC Billet Rods do not have forced oil dippers * ARC Billet Connecting Rods, Briggs Flathead 3.870" X .4908 SS Special ENDURO Standard Stock Stroke for the flathead this rod is WKA & IKF Legal