This is an MR33 Clamp Servo Horn Offset (19/15mm) (25T)
Fits servos with 25 teeth (Futaba, Power HD, Savöx, etc). Aluminum servo arms will make the steering more responsive compared to a plastic arm or a servo saver. The Servo Horn has an additional little screw which gets tightened from the side to eliminate unwanted play. The two mounting holes for the ball stud (19 and 15mm) offer two different setting options.