ABSTRACT: This is the user guide of the Maury Microwave AFTNC Coaxial Calibration Kit for models 8680CK10/11 and 8680CK20/21. This series of AFTNC the DC to 20.0 GHz coaxial calibration kits is designed to provide accurate calibrations of network analyzers in range. Each of these kits includes all the necessary calibration standards and associated hardware needed for the accurate calibration of most network analyzers.