Aluminum connectors accept both aluminum or copper wire while copper connectors accept copper wire only and all 1-piece tin plated|Connectors are all 1-piece tin-plated|Insulators are virtually unbreakable, made of glass-filled polycarbonate|See-through, hinged safety covers provide a greater degree of safety and shock resistance where required|Hinged covers can be installed without tools|1 in through air and 2 in over surface between uninsulated live parts of opposite polarity meets requirements for feeder and branch circuit applications of UL508A|Polycarbonate safety covers provide dead-front protection|One cover is needed for each pole|Each cover has a test probe hole in the center for circuit checking|Adder poles for increased flexibility and ease-of-use|Adder poles can be stacked to form multi-pole units in the field without the use of tools|Adder poles allow for customization of primary and secondary wire combinations|14 to 4 AWG Al line/load