MY use is to allow me to use my 2 pin circuit indicator on light outlets. What you see in the photos is a socket adapter connected to a "transmitter" for a circuit tracing tool (the receiver is shown on the side). The polarized nature of these screw plug adapters is a huge plus over older designs. Polarization means you keep track of which wire is the 'hot' wire and which is the reverse, helping to avoid accidental bumps from old things like vintage lamps etc to make good contact. They also seem to be durable. The price, as stated in the test report, corresponds to a multipack.
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