Originally created to produce connecting rods for a vintage Ossa, Hot Rods has grown to become the world's largest supplier of O.E.M. replacement crankshafts and performance gaining stroker crankshafts. 65.5 mm stroker piston. Increases displacement to 391cc. Sold individually (application may require two). Installation note: Must be used with Hot Rods +5 mm / 4 mm Stroker Crank or +5 mm Long Rod Crank.