The 21XZ-B Speed Spec II is available in a special Gold Edition to commemorate O.S.’s 80th anniversary. A gold cylinder head and carb insert makes it extra-attractive for collectors, while the legendary O.S. performance makes it a must for high-octane racing. Some other features include a lighter crankshaft, with DLC coating, tungsten weighting and silicone-filled intake passage. There is also a modified piston and con rod that reduces overall weight.