Paul, Hensley used Adapt-a-Ball for the first few years, through about the early '90's. The Adapt....... had a hexagonal (6 sides) stud welded to the top plate. They used that design for the consumer. You could use fhe 2 5/16 ball or pull the pin and use another size ball. About 1987, Adapt......went out of business, but some companies still had their hitch balls; Hensley was one of them, and I received one of their designs in 1997. After that, Hensley welded the ball to the top plate. Hensley is a great company and makes a remarkable hitch. Even with the problems that I'm having, I'd never use any hitch but a Hensley.