1、With waterproof design, suitable for indoor/outdoor or ocean use. 2、Built-in overload, over-current and short circuit protection, very safe to use. 3、UV stabilized nylon housing with rubber splash-proof & tight-fitting front cap. 4、Voltmeter with three digit LED digital display, real time monitor the battery voltage. 5、Mounting screw and labels included, easy to install, can be installed horizontally or vertically. Features: With waterproof design, suitable for indoor/outdoor or ocean use. Built-in overload, over-current and short circuit protection, very safe to use. UV stabilized nylon housing with rubber splash-proof & tight-fitting front cap. 2 pole nickel plated brass terminal connectors Mounting screw and labels included, easy to install, can be installed horizontally or vertically. Use on automotive electronic field, electrical devices, most car, truck, buses, SUV, home, boat, camper/RV, ATV, UTV, golf cart, and more electrical devices. Can be used to charge for mobile phones, tablet, GPS, digital cameras, PDAs etc. Specification: Material: Nylon Item Color: Black LED Color: Green USB Output Current: 3.1A（2.1A/1A) Interface: 2 USB Voltmeter Display Range: 0-35V DC, 10A Voltmeter Mounting Hole: 29mm Size: Shown as Picture Package Weight: approx.355g/12.5oz Fitment: universal for 12-24V car, boat, marine, RV, truck and etc. Package list: 1 * USB Charger with Voltmeter(As picture shown) 3 * Cables 9 * Blue Terminals 4 * Screws