Speedmaster™ flywheels are fully CNC machined from a high tensile aircraft billet steel. The high carbon steel material is incredibly strong and can withstand the rigors of the most extreme engines, drivers, and road conditions. Grab one of these race-ready Speedmaster™ billet steel flywheels for the durability and performance that you demand at a great price! To withstand the severe abuse of high-rpm racing in heavy drag cars, use Speedmaster™ billet steel flywheels. Most are drilled for both Borg & Beck and Long-style clutch assemblies.