Kewtech Kewcheck R2 Mains Tester Socket Adaptor 4mm
The device is compatible with all standard 4mm test probes, and when in use it'll allow you to use your testing equipment to perform R2 and R1 + R2 measurements as well as detect voltages.
The obvious main benefit of this product is that you don't have to remove the socket covering to actually perform testing - instead simply hook up your test meter with 4mm probes, plug the probes into the Kewtech R2 and you'll be able to check the wiring's internals.
The KEWCHECK R2 is compatible with most insulation/continuity and multifunction testers from manufacturers such as Megger, Seaward, Fluke, Robin, Metrel, DiLog and many more.