When choosing a clutch it is very important to match the appropriate horse power and work load. For example: The MU 0090 Rally and MU 0090 Con O are capable of handling the horse power and torque ratings provided in our listings, but if the truck is used for heavy hauling when coupled with torque ratings exceeding 600 ft. lbs. damage to the clutch disc WILL occur. The cause and effect is the 12 1/4" disk does not provide enough dampened area to absorb the added torque of the Cummins along with heavy hauling. These two clutch kits are fine for light towing and performance. If you are going to be towing in excess of 8,000 lbs. while exceeding 600 ft. lbs. of torque you must go with the MU 13-1.25 Con O, OFE or FE. This will offer a clutch that will handle heavy towing with vehicles equipped with the higher torque ratings. This clutch only applies to trucks with 5 speed transmissions and early 6 speeds that are not equipped with the HO engine. If a 12 1/4" clutch is purchased from us and gets destroyed at the dampened portion of the disc, warranty will not be granted.