Just to clarify a few things. The "11" at the end of ZFR5F -11 actually means 1.1 mm or .044". Where does .038 to .042 come from? Secondly, the thread size is 14mm which requires a torque of between 18 and 21 lbs per ft. Where does 13 come from? Can someone elucidate?

 

the .038-.042 is how much gap distance between the electrode and the tip of the plug should be.

 

The 13 is Honda's recommended torque for the plugs.