Hello. I have two calibration kits of the same model. They both pass their pin depth and electrical specifications. However, I tend to get slightly better measurements with one kit versus the other when measuring the same device. If I perform a VNA verification using each calibration kit and compare the results of the 20 and 50dB attenuators, and the airlines, how much difference should be expected? And, is it valid to use an airline, termination, and offset short to measure the directivity and source match of the VNA and deduce that the one that yields the better results is the better calibration kit?