Fits all your needs. 3 terminal for metal frame ground systems, 4 terminal has insulated ground terminal for use with fiberglass or other non-conductive materials. These switches have cadmium plated, non-breakable heavy duty housings. They resist rust, and give long life in most any environment. They isolate the starting battery, assuring you of primary battery power for starting the engine. Has full time charging of both batteries. Includes terminal nuts and lock-washers. For 12VDC continuous duty.