Aluminum-to-copper twist-on connector hexagonal head for easy installation by hand or with a standard nut driver Corrosion-resistant compound penetrates corrosion build-up on aluminum conductors for conductivity and cool connections. Filled connectors are designed to be used only once. Minimum capacity of 1 #12 aluminum wire with 1 #18 copper wire, Maximum capacity of 1 #10 aluminum solid wire with 2 #10 copper solid wire Live-action square-wire spring expands and contracts with the aluminum wire, compliant with NEC Section #110-14(b) for aluminum-to-copper connections UL 94V-2 flame-retardant shell rated at 221 degrees F