The ZD-4-X from MCLI is a RF Detector with Frequency 10 MHz to 18.5 GHz, Max Input Power 23.01 dBm, Frequency Flatness ±0.5 dB, Voltage Sensitivity 500 mV/mW, VSWR 1.50:1. Tags: Module with Connectors, Diode Detector. More details for ZD-4-X can be seen below.