Frequency Meter Smart Look Series 120V AC INPUT Scale: 55-60-65HZ 3.5 inch The Smartlook range of Analog Panel meters offer accurate measurement and indication of most  electrical and electronic parameters in industry standard 2½” and 3½” case sizes. This innovative  design features a detachable lower fascia plate  which allows the flexibility of either surface  or window mounting. The fascia is simply unclipped  to achieve the completely flush panel appearance  of panel window mounting. The range offers AC and DC Ammeters, Voltmeters and frequency meters utilizing  a high torque scale value and features a rear zero  adjuster screw for tamperproof installation.  AC moving iron meters provides high  accuracy true RMS measurement of 1.5%.