This electrical adapter is designed to adapt a 4-way flat vehicle socket to fit a 5-way flat trailer plug. It is specifically intended for boat trailers with surge brakes, adding in a fifth wire for the reverse lights and allowing your vehicle's 4-way flat to easily plug into your boat trailer 5-way flat. This boat trailer wiring adapter features durable molded plastic construction and requires some splicing. All CURT wiring and electrical products come with a one-year limited warranty to give you the assurance you need to tow with confidence.