CURT 57672 Dual-Output 4-Way Flat Vehicle-Side to 7-Way RV Blade Trailer Wiring Adapter

Can you measure the opening of the wiring receptacle to the left of the hitch receiver pictured above? I'd like to see if it can fit this Curt 4-pin-to-7-pin receiver. The receiver has a flip cover and it appears to be 3 inches square. I'm worried that the flip cover won't work. https://www.amazon.com/57672-4-Way-Dual-Output-Electrical-Adapter/dp/B001EP0HPI/ref=ast_sto_dp_puis