A 4-flat-to-6-round trailer adapter connects a vehicle’s 4-way flat wiring to a trailer’s 6-way round socket, but the right choice depends on whether you need a simple converter or more than one towing option. The NEW SUN adapter is best for buyers who want a short pre-wired harness and bracket. The CURT 57183 suits those who want a covered 6-way socket, while the CURT 57604 and Hopkins Multi-Tow provide both 4-flat and 6-round options. The CURT 57620 is included as a reverse-direction alternative, not as a match for the requested conversion.
| Adapter | Best For | Direction |
|---|---|---|
| NEW SUN 12-inch harness | Pre-wired installation | 4-flat to 6-round |
| CURT 57183 | Covered 6-way socket | 4-flat to 6-round |
| CURT 57604 | Two trailer connection options | 4-flat to 6-round and 4-flat |
| Hopkins Multi-Tow 64 | Dual-output towing | 4-flat to 6-round and 4-flat |
| CURT 57620 | Opposite connector direction | 6-round vehicle to 4-flat trailer |
NEW SUN 12-Inch 4-Flat To 6-Round Harness
This NEW SUN adapter is best for buyers who want a pre-wired harness with a bracket as part of the connection setup. It converts a 4-way flat connector to a 6-way round socket and has a listed 12-inch harness. Its socket is made with zinc die casting, and the product description lists copper connector pins and wiring with anti-rust features.
Choose this if a short harness and bracket suit your installation needs. The listing describes straightforward setup, but it does not specify that the adapter supplies every circuit a 6-way connection may support. Confirm wiring functions before relying on trailer brakes or auxiliary power.
CURT 57183 4-Flat To 6-Round Adapter
The CURT 57183 is best for a buyer who needs a direct 4-flat-to-6-round connection and wants a spring-loaded dust cover on the round socket. The cover is intended to help protect terminals from water, dirt, and corrosion. The adapter is listed for standard 4-way flat connections.
Its 6-way socket can be used for lighting and may connect trailer brakes or auxiliary power, but the product details say some splicing is required for those functions. Choose it for the covered socket; avoid assuming a plug-in connection alone activates every 6-way circuit.
CURT 57604 Dual-Output Adapter
This CURT adapter is best for buyers who want to retain a 4-flat connection while adding a 6-round socket. Its dual-output design offers both connection types from a 4-flat input. The listed features include dust covers for both sockets and a slit loom sleeve to protect the wiring harness.
Choose this if you tow trailers with different plug styles and want both outputs available. The description notes that some splicing is required for trailer brakes and auxiliary power. Check the trailer and vehicle wiring before expecting those circuits to work.
Hopkins Multi-Tow 64 Adapter
The Hopkins Multi-Tow 64 is best for a buyer seeking two towing options from one vehicle-end connector. The listed configuration provides a 4-wire flat connection and a 6-round adapter. This makes it a practical candidate when a vehicle has 4-flat wiring and the driver wants to connect trailers with either listed plug style.
The product information is brief and does not specify additional details such as a dust cover, harness length, or circuit-by-circuit wiring instructions. Choose it when the dual-output format is the main requirement, and verify the connection and functions needed for your trailer before towing.
CURT 57620 6-Round To 4-Flat Adapter
This adapter is included as a direction check, not as a substitute for a 4-flat-to-6-round converter. It is best for someone whose vehicle has a 6-way round socket and whose trailer has a 4-way flat plug. Its ergonomic side tabs are designed to help with gripping, plugging in, and unplugging.
Choose it only when the vehicle and trailer connector directions match that setup. Avoid it if your vehicle has a 4-flat connector and your trailer needs a 6-round socket; this model converts the opposite way.
Buying Guide: How To Choose A 4-Flat-To-6-Round Adapter
Which connector is on the vehicle and which is on the trailer?
Start by identifying both ends. A 4-flat-to-6-round adapter takes a 4-way flat vehicle connection and provides a 6-way round socket for a trailer plug. Direction matters: an adapter designed for a 6-round vehicle socket and 4-flat trailer plug will not perform the requested conversion.
Do you need one output or two?
A basic adapter, such as the NEW SUN harness or CURT 57183, provides a 6-round connection from a 4-flat input. A dual-output option, such as the CURT 57604 or Hopkins Multi-Tow 64, is worth considering if you also need a 4-flat connection available.
Will the adapter provide trailer brakes or auxiliary power?
A 4-way flat connection generally covers lighting functions such as tail lights, brake lights, and turn signals. A 6-way round connector has additional circuit positions, but an adapter does not necessarily supply those functions by itself. The CURT 57183 and CURT 57604 listings specifically note that some splicing is required for trailer brakes or auxiliary power. Confirm your wiring setup before towing.
Are weather protection and installation details important?
Compare socket covers, harness layout, and installation requirements. The CURT 57183 has a spring-loaded dust cover, while the CURT 57604 lists covers for both sockets and a protective loom sleeve. The NEW SUN model lists a 12-inch harness and bracket. Match these details to your vehicle’s mounting location and use.
Frequently Asked Questions
What does a 4-flat-to-6-round adapter do?
It connects a 4-way flat vehicle-side connector to a 6-way round trailer connection. It changes the connector format, but additional wiring may be needed for circuits beyond basic trailer lighting.
Can a 4-flat adapter power electric trailer brakes?
Not necessarily. The adapter’s extra connector positions do not guarantee that brake wiring is present or active. Check the product instructions and vehicle wiring; some listed adapters require splicing.
Should I choose a dual-output adapter?
Choose a dual-output model if you want both a 6-round socket and a 4-flat connection available from the vehicle-side setup. If you only need a 6-round socket, a single-output adapter may be a simpler match.
Will a 6-round-to-4-flat adapter work for this setup?
No, not if the vehicle has a 4-flat connector and the trailer has a 6-round plug. That adapter is designed for the reverse direction, so check the connector positions before purchasing.