A ground fault circuit interrupter(GFCI)shuts down power in milliseconds when it detects the tiniest change in current flow. Codes require GFCIs in bathrooms, in kitchens near sinks, outdoors, and in garages. GFCIs are inexpensive and simple to install. A single GFCI can protect up to four receptacles,switches, and lights on the same circuit. A GFCI circuit breaker can protect an entire circuit. If your home has ungrounded receptacle, installing GFCIs will provide protection, but won"t ground your circuits. Check your GFCIs at least once a month by pushing in the test button.(The reset button should pop out. Push it back in.) A GFCI may provide power even though it has lost its ability to protect. Don"t use a GFCI as a receptacle for a refrigerator, freezer, or any other appliance that must stay on all the time--it may trip off without your knowledge. Also do not attempt to control a GFCI with a switch.---Shipping via China Post, it takes 7-10 business days to delivery.