This is a ProTek R/C Aluminum Servo Horn, and is intended for use with any servo that uses a 25 tooth spline output shaft.
Features:
19mm hole spacing (measured from output shaft screw hole, to linkage rod holes, center to center)
3mm thick arm
27.25mm Overall length
Linkage holes threaded for 3mm hardware
25T Spline Futaba/Orion/Savox/ProTek Output Shaft