7 Way to 4 Way Trailer Plug Adapter, Waterproof 7 Pin Blade to 4 Pin Flat Trailer Plug, Trailer Plug Adapter Round Connector Accessories, Universal for RV Truck Trailer Tow Hitch (Black). Premium Material Construction: This trailer plug adapter is manufactured from high-strength ABS plastic material, known for its outstanding durability and resistance to water, high temperatures, abrasion, and corrosion.