The Q-Lok Pro attaches to any cable size from 16/2 to a heavy duty 10/3 with its standard 5/8” thickness. For cords from 16-12ga. 300v. the Q-Lok Pro uses a variable diameter cord restraint. This eliminates the common unsafe frayed cords, broken insulation on the wires both outer and inner. It is one of the very few devices in the world that has this cord restraint feature.