CURT 2 in. Square 2 Hole Trailer Hitch Ball Mount, 4 in. Drop 45230
Amazon.com: OPENROAD Adjustable Trailer Hitch Ball Mount Fits 2-Inch Receiver, 2" Tow Balls 7500lbs, 9-1/2" Drop/ 8-1/4" Rise Drop Hitch, Tow Hitch for Heavy Duty Truck with Stainless Steel Pins and Lock :
Amazon.com: B&W Trailer Hitches Tow & Stow Adjustable Trailer Hitch Ball Mount - Fits 2" Receiver, Dual Ball (2" x 2-5/16"), 3" Drop, 10,000 GTW - TS10033B : Automotive