CURT 7-Way Round to 4-Way Flat Trailer Wiring Adapter — 7-to-4 Converter, Plug-and-Play Black Plastic

CURT 57041 is a plug-and-play wiring adapter that converts a 7-way round vehicle socket into a standard 4-way flat trailer plug so you can power basic trailer lights without cutting or splicing wires.

When your tow vehicle and trailer use different connector styles, you don’t need to rewire either one to get lighting and signaling working. The CURT 57041 adapter bridges a 7-way round vehicle-side socket to a 4-way flat trailer-side plug, delivering tail lights, brake lights and turn signals through a durable, weather-resistant black plastic housing. Installation requires only plugging the adapter into the vehicle socket and inserting the trailer’s 4-flat plug into the adapter—no tools or wire splices required.

How does this adapter simplify towing with mismatched connectors?

The CURT 57041 eliminates the need to rewire or buy a new harness by adapting the vehicle’s seven-pin round output to the trailer’s four-flat input. It’s ready to use right out of the box so you can connect and tow in minutes.

• Converts 7-way round vehicle socket to 4-way flat trailer plug
• Plug-and-play—no cutting, splicing, or additional wiring
• Works with standard lighting functions: tail, brake, and turn signals
• Compatible with most trailers that use a 4-flat connector

Will the adapter handle exposed or frequent outdoor use?

CURT designed the adapter with a robust black plastic body that resists rust and corrosion compared to metal housings. While not a sealed waterproof device, its construction stands up to regular towing exposure and typical road conditions.

• Durable plastic housing reduces corrosion risk
• Side grip tabs make insertion and removal easier in tight spaces
• Compact form factor stores easily when not in use
• Backed by a one-year limited warranty for peace of mind

What electrical functions are supported by this adapter?

This adapter passes the basic lighting circuits required for safe road use: running lights, brake lights and turn signals. It does not transmit auxiliary circuits such as reverse lights, electric brakes, or 12V accessory power that rely on extra pins in larger connectors.

• Transmits tail/running lights
• Provides brake light signal
• Passes left and right turn signals
• Does not provide electric brake or auxiliary power lines

Who is this for? The CURT 57041 adapter is ideal for vehicle owners who occasionally tow trailers fitted with a 4-flat plug but drive a tow vehicle equipped with a 7-way round socket. It’s also a practical accessory for rental trucks, service fleets, and DIYers who prefer a no-fuss, removable solution rather than altering factory wiring. If you need a simple, temporary, and durable way to match two common connector standards for lighting functions, this adapter delivers fast compatibility without permanent changes to either the vehicle or trailer.