This adapter allows connection of either 4 or 5-way flat trailer plug to vehicles with 7-way receptacles. It is designed for use with boat and utility trailers with certain hydraulic surge brakes and /or backup lights. Designed for use with boat and utility trailers. For use with hydraulic surge brakes and/or back up lights. Compatible with plastic or metal connectors. Features non corroding brass contacts. WARNING: This product can expose you to chemicals including DEHP which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov. -