I reached out to my contact at Pollak and the Mounting Bracket and Installation Hardware - Pollak 7-Pole, RV-Style Trailer Connector - Vehicle End # PK12711U you were looking at includes four 3/16" x 5/8" long screws, four 3/16" nuts, and two #8 x 1/2" long self tapping screws.
I included a video of the # PK12711U for you to take a look at. view full answer...
The Optronics HyperX LED Trailer Tail Light # STL572RB comes as a single light. You would need to order a quantity of two for a pair of the # STL572RB.
To wire it to your trailer you'll also need the 3-Wire Pigtail # A45PB. view full answer...