Shop straight-tongue, A-frame and adjustable couplers spanning roughly 2,000 to 25,000 lbs capacity, with 1-7/8 in., 2 in. and 2-5/16 in. ball diameters and various channel widths. Brands like Bulldog and Fulton offer sleeve-lock, easy-lock and posi-lock designs, plus repair kits, hinge kits and mounting hardware for existing couplers.