The Agilent 8478B provides high efficiency and good radio frequency (RF) match. Used in conjunction with the N432A or 432A power meters they provide high accuracy even in routine power measurements. These thermistor mounts are temperature compensated for low drift, even in the presence of thermal shocks, permitting measurement of microwave power as low as one microwatt. Each mount contains data showing calibration factor and effective efficiency at six frequencies, directly traceable to the U.S. National Institute Standards and Technology (NIST) at those frequencies where NIST provides calibration service.