Review on Songhe FM Transmitter Pickup Module - Mini Wireless Microphone for FM Emission - Wireless Audio Transmitter MIC Core Board V4.0 by Giovanni Glenn

The only clues are in the product description in the listing, not the device. Pretty easy to set up. I used a lithium cell for the power supply, about 4 volts. Added an antenna as suggested and set the radio to a quiet spot around 108. Use a tiny screwdriver to adjust the cap until I heard feedback. Anyway, the microphone overloads the transmitter, I had to keep the radio volume down, but I'm very happy with the price and performance. I haven't tested the full range but will work on my porch and garage at least 50 feet from the radio. For less than $5, good performance and I would buy again.