Meets the 29.3 SFI Approval This is a must with the high torque Cummins in conjunction with a better designed torque converter that can transfer the torque with no slip. The flex plate is bolted to the crank shaft, then the converter is bolted to flex plate. The torque from your Cummins is transfered to the flex plate, from the flex plate to the torque converter then to your input shaft in the trans. With increased torque from the engine and no slip out of the converter it can crack and/or rip the center out of a stock flex plate. The Sun Coast billet flywheels are CNC machined from a forging for strength and reliefs are machined out between the converter mounting area and the crank flange to enable some flex. We designed our flexible billet flywheel with the understanding that it needs to flex but at the same time we added extra thickness to prevent cracking. We started with a better quality material and a better manufacturing process to make it stronger. Our flexible flywheel made or exceeded all the new SFI specification 29.3 requirements for materials, mechanical properties, design and rotational integrity. NOTE: A SFI certified flywheel flex plate is required on drag racing vehicles running 11.99 and quicker in the 1/4 mile and 7.49 and quicker in the 1/8 mile, or any vehicle exceeding 135 mph. It was changed in 2008 from the 29.1 SFI specification to the SFI specification 29.3 for automatic transmission flex plates for diesel applications. The new rules for the flexplate requires that the material can not be a stamped metal as many OEM and aftermarket flex plates are. To maintain the SFI specification 29.3 requirements, the flex plate must be replaced every three years.