connectors are either copper or aluminum, based on requirement. Check Out these Quality Park Features All breakers are bussed, including main breakers no wires All bolt-on breakers... lugs, feed thru lugs, split bus, remote control switches, time clocks, rainproof enclosures and service entrance label Extruded branch bus has case hardened thread forming screws... gutters and pull space for handling larger wire sizes Directory frame mounted on the door Unique branch neutral accepts a range of aluminum or copper wire sizes from #14 to #1/0...