Left one:

Straight Tongue Trailer Coupler for 2-Inch Channel, 2-in Hitch Ball, 3,500 lbs

Middle one:

50mm Trailer Hitch Trailer Coupling Hitch With Integral Lock 3500 lbs

Right one:

A 50mm heavy-duty ductile iron ball coupling suitable for use with electric trailer brakes. ADR rated to 3500 lbs for on-road applications.