This Rubber Grommet and Plug combination is perfect for mounting 2" round lights to your trailer. The plug fits lights with the standard two male non-polarized posts. This open-back style grommet is typically used on sealed light units when a splash place is not present, and will fit in 2 5/16" mounting holes up to 1/4" thick. These can be used to install side marker lights to the side of your trailer, or brake lights to the rear of your trailer, and are compatible with either LED or incandescent lights.
An example of what type of light this setup is designed to work with can be found here.
For installing 2" Round Lights
Fits a 2 5/16" Mounting Hole
White Wire is Ground
Black Wire is Power