The Masterplug MSTARCDKGMP safety RCD adaptor plug simply plugs into the mains, and then you plug your electrical appliance into it. If there is a fault or a short in the tool you are using, the unit cuts the power very quickly, reducing the risk of electrocution.The Masterplug safety RCD adapter continuously monitors the power supply to an electrical appliance and cuts off the power within 40 milliseconds if an earth current fault is detected. This is fast enough to prevent a fatal electric shock. This plug is an ideal way to protect yourself when using portable electrical tools such as lawnmowers and drills.Electrical appliances can become dangerous if the wiring becomes loose, their power cords become damaged or if they get wet. Not only power tools and lawnmowers can cause electrocution--it is also possible if fingers, wet hair or other conductive bodies enter the appliance. In all these cases the Masterplug safety RCD adaptor is a must. RCD adaptors are the simplest way of power protection for in and around the home. Ideally, you would use an RCD adaptor with any electrical appliance. Please note, these products are not suitable for pond pumps and other pond equipment as when these are removed the installation is unprotected.