"Material: The shell is made of high quality plastic, copper terminals with iron hex nuts for improved continuity, high temperature resistant, not afraid of falling, durable. Function: Used for the battery to insulate and secure the electrical System, to eliminate all power consumption from the battery when the vehicle or boat is not in use, to safely disconnect the battery. Additional Protection: The battery master switch comes with 2 keys and a weather cover, and the keys also cover the opening when in use, which can better protect dust and water entering the keyhole. Size: The screw diameter is 8mm/0.31 inch and the installation opening is 5mm / 0.20 inch The battery switch is used for DC 12V, rated current: 300A (12V). Wide applications: It can be used as an opening key for various electrical devices such as speed cameras, chassis and fog lights , which can be used indoors and outdoors."