Curt 57187 Flat Adapter 4-Way to 5-Way for Boat Trailer Surge Brakes

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Item Description

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.

  • Adapts vehicle 4-way flat to plug into boat trailer 5-way flat
  • Intended for boat trailers with surge brakes
  • Fifth wire splices in to connect reverse lights
  • Adapts 4-way flat vehicle socket to fit 5-way flat trailer plugs
  • Durable molded plastic housing resists corrosion


  • Some manual wiring required