1.) Internal connections with high-quality copper, good conductive properties, effectively preventing arc generated, not loose in normal use. 2.) Inner shell is fireproof PA66, doesn't burn in 750° C high temperature. 3.) Using high standard copper wire, well conducted, less heat, more secure in using, 4.) L&N double break switch with silver alloy contacts and LED indicator 5.) Optimized copper structure ensure excellent insertion and Extraction performance.