Something like one of these pics. It should have a ball link and HD arm on the servo end. The control surface end is fine with a stock horn but not a ball link. The clevis will give you a straight push/pull. The ball link will twist the horn under any kind of load. Try turning your radio on and giving the surface full deflection. Now push on the surface. You will see the horn twist. Eventually the horn will break. You may want to start with new horns when you change to a clevis. This is a common mistake I have seen a lot. Ball links are great for getting the slop out of a system. This is just not the proper place to use one.
Trying to teach not preach, David