It is .029". That is with a "factory" gearset. That is with a perfect 0.000" machined housing and a gearset marked -0 or +0. The problem is the housing is not marked ever! The only way to determine the housing mis-machine is to do the math on a rear that has never been apart and never had noise. Say you tear down a rear and the gearset is marked -2 and the shim is a .027", that means the housing is mis-machined .004" shallow. Or if it marked +2 and the shim is .027 the housing is perfect .000". If it is marked +2 and the shim is .031" is housing is .004" machined to deep. This all goes out the window if you are using a aftermarket gearset marked with a pinion depth number. You then need a set-up to measure pinion depth, then shim, then recheck. I have been setting up Chrysler diff's since 1975 and the I have never been able the "read" the marking compound method. I have even tried reading the marking compound pattern then checking it after using the pinion measuring tool and found the two methods not even close. I hope this helps you.