CURT Trailer-Side 7-Pin Round Wiring Harness Socket with Spring Model 58181CURT Trailer Side 7 Pin Round Wiring Harness Socket with Spring Model 58181 Like trailer hitches and ball mounts, electrical connectors range all over the board in shape, size and capability, but no matter what your trailer's electrical functions are, you need a solid connection to keep the power flowing and ensure safety on the road. CURT electrical connectors are designed and manufactured to give you a reliable connection every time you plug in your