Weather-resistant: meets national electrical code; weather-resistant requirements. Tamper-resistant: meets national electrical code; tamper-resistant requirements. Protects children: patented shutter system helps prevent improper insertion of foreign objects. Listed to the weather-resistant supplement of UL498 meeting demanding UL requirements including: ultraviolet light exposure test; cold impact test; accelerated aging test; stringent material requirements for current-carrying parts, wire binding screws and mounting straps to ensure superior corrosion resistance. Conducts an automatic test every three seconds, ensuring it's always ready to protect. If the device fails the test, the indicator light flashes to signal that the GFCI should be replaced. It also has our proven safe lock protection feature: if critical components are damaged and protection is lost, power to the receptacle is disconnected. Thinner than competitors' GFCI receptacles: leaves more room for wires in the box. Auto-ground clip assures a positive ground to metal box. Meets 2015 UL requirements. Feed-thru wiring configuration allows GFCI to protect downstream receptacles. Prevents line-load reversal miswire: no power to the face or downstream receptacles if wired incorrectly. Exceeds UL 943 voltage surge requirements; survives 100x the required UL 3Ka/6Kv voltage surge test cycles. Trip indicator light (red LED). side or internal screw-pressure-plate back wire with #10-#14 AWG solid or stranded copper wire.