Advantages: Small area, so you can install two on a normal single socket. Appears to be well put together, a cut above the unnamed material of dubious provenance and attention to the electrics. Code/Security. It is EXTREMELY easy to disassemble and flash the Tasmota/ESPHome when you need it. Easily integrates with Home Assistant and displays history of energy consumption, power, apparent power, reactive power, power factor, voltage and current. Cons: I ordered five units; (four S31s and one S31