Description: Twist of knob disconnects power. It is made of copper. Enables you to quickly and easily disconnect your automobile battery for safety, servicing or storage. Battery operated switch to engage power just hand tighten the black knob,slightly loosen it to disconnect all power. Perfect for car, truck, boat or RV battery. Specification: Material: Copper Size: 102x37x35mm/4.01x1.45x1.37inch Package Includes: 1 Piece Battery Disconnect Switch