For connecting measuring devices to RCDs, RCCBs, GFCIs, circuit breakers, etc., without loosening their screws (the screws must be made of iron or steel). Designed to create safe semi-permanent (lasting a few hours) connections between 4 mm banana plugs and the iron or steel screws of RCD, RCCB, GFCI, and protective switch terminals, without loosening them. The magnetic tip allows this adapter to adhere to screws or other electrical contacts that are largely made of steel, iron, or nickel (ferromagnetic materials). Typically found on the screws of certain circuit breakers and residual current devices. The magnetic strength depends on the shape and material of the contact. The magnetic strength is lower with a steel screw that has a lens head compared to a steel screw with a flat head. Therefore, it is important that the contact is at the bottom of a cavity with an inner diameter equal to or greater than 6.7 mm, but close to 6.7 mm.