Feature: 1. Smart Charging: Automatically merge two batteries when charging, and automatically isolate two batteries when not charging. 2. Stable Working: Has a voltage sensitive chip to ensure your main battery will provide strong power for vehicle operation. 3. Extensive Uses: Allows for wide use on campers, for 4x4, recreational vehicle, marine application and so on, very practical. 4. Reliable Using: This dual battery isolator relay can also withstand extreme weather, shock, and it's waterproof as well. 5. Easy to Install: There are 4pcs screw and 1pc terminal in the set, bringing more convenience to the installation. Specification: Item Type: Dual Battery Relay Product Material: ABS Colour: Black Continue Rated Value: DC 125A Intermittent Rated Value: DC 140A Binding Post: M6 (1/4in) Waterproof Grade: IP67 Application: Suitable for installation on campers, for 4x4, recreational vehicle and marine application. . Package List: 1 x Dual Battery Relay4 x Screw1 x Terminal1 x English User Manual