These coaxial shorts are usefull to establish a reference plane, as well as providing certain protections from the environment. SMA shorts and Type N Shorts can establish reference planes. These coaxial shorts are not VNA grade but are often used at lower frequencies for calibration purposes. TNC shorts, BNC shorts, SMA shorts, & N shorts are also useful for TDR measurements. New are 2.4mm shorts and 2.92mm shorts.