I agree with RCIGN1, From personal experience!! (trashed all 6 bolts and disintigrated prop) I have purchased a reliable torque wrench and now religiously check ALL my engines before flight for proper fit and tightness on each prop.The power that these motors are putting out will easily break props and prop bolts if the proper tension on the bolts is ignored or GUESSED at !! Too loose and it becomes sloppy, Too tight and your stretching the bolts to a certain extent which eventually will cause failure.Overtightening is just as bad as undertightening especially in the larger horsepower engines.