Teradyne tester specifications list instrument capabilities and limitations, and the accuracy of instrument parameters. Words like guaranteed, typical, and measured are defined by the specifications, and manufacturing each instrument includes measuring the values noted in the specifications. Using the UltraFLEXplus as an example, this presentation will address what is specified, and what is not, and review the specified calibration process to ensure specified parameters continue to be accurate, enabling the user to design accurate testing and guide them to appropriate guard banding.