Oyviny 7-Pin to 4-Way Flat Trailer Wiring Adapter — Zinc Die-Cast Housing, Weather-Resistant

The Oyviny 7-Pin Round to 4-Way Flat Trailer Wiring Adapter converts a vehicle-side SAE J560 7-way round socket into a standard 4-way flat trailer plug for reliable towing connections.

When a tractor, semi, dump truck or RV has a 7-way round SAE J560 outlet but your trailer uses a 4-flat wiring harness, this adapter provides a quick, durable, plug-and-play bridge without any rewiring. Built with a corrosion-resistant zinc die-cast 7-way housing, a nylon wire loom and a rubber dust cap for the 4-flat plug, it’s designed for frequent outdoor use and heavy-duty towing scenarios.

How do I connect the Oyviny adapter to my vehicle and trailer?

Connecting the adapter is straightforward: insert the 7-way round plug into your vehicle’s SAE J560 outlet and plug the 4-way flat connector into the trailer harness. The ergonomic handle hooks make gripping, aligning and removing the adapter easier, so one person can complete the connection quickly.

• 7-way round plug matches SAE J560 vehicle sockets used on trucks and tractors
• 4-way flat connector accepts standard trailer tail/brake/turn wiring
• Ergonomic handle hooks on both sides for secure plug/unplug
• Installation usually takes less than two minutes—no tools needed

Will this adapter provide all the lights I need for legal towing?

The adapter carries the basic four circuits: running lights, left and right turn signals, and brake lights. It does not carry auxiliary circuits such as electric brakes, reverse lights, or battery charge functions, so trailers that need those features require a different 7-way to 7-way solution or an additional wiring harness.

• Supplies tail/ brake/ left & right turn signal circuits reliably
• Not intended for electric trailer brakes or auxiliary power circuits
• Use for trailers with a 4-flat system—boats, utility trailers, small campers
• Weather protection reduces corrosion risk for consistent light operation

What materials and protective features improve durability?

The Oyviny adapter is engineered for outdoor and heavy-duty use. The 7-way vehicle-side housing uses zinc die-cast metal to resist corrosion and impact, while the cable bundle is sheathed in a black nylon loom to prevent chafing. The 4-flat plug includes a rubber dust cap to keep moisture and debris out when the adapter is idle.

• Zinc die-cast 7-way housing resists rust and mechanical wear
• Nylon wire loom keeps wires tidy and protected from abrasion
• Rubber dust cap shields 4-flat terminals against water and dirt
• Rugged construction suited to farm, highway, and marine environments

How do I know this adapter fits my truck or trailer?

The adapter was made to interface a vehicle-side SAE J560 seven-pin round socket with a standard four-pin flat trailer connector. Confirm your vehicle has a SAE J560 7-way round outlet and your trailer uses a 4-flat plug; if so, compatibility is ensured. If your trailer requires additional circuits, consider a different adapter or add-on wiring.

• Compatible with U.S. vehicles equipped with SAE J560 7-way round sockets
• Works with trailers using a standard 4-flat wiring system
• Not suitable if your trailer needs electric brakes or auxiliary power
• Simple visual check: round seven-pin outlet on vehicle, flat four-pin on trailer

Who is this for: The Oyviny 7-Pin Round to 4-Way Flat Adapter is intended for drivers who tow smaller trailers from trucks, tractors, dump trucks or semis that have a 7-way round SAE J560 socket but need the basic 4-flat lighting circuits on their trailer. It’s a practical, durable choice for farmers, boat owners, utility contractors and fleet operators who require a fast, no-rewire connection that stands up to outdoor conditions.