Used in the steering gear output shaft or DC motor shaft, drive to play the role of the fixed side of the hole with the top wire.You can also do the crank rod. SpecificationsMaterial: CNC AluminumHead with a M3 Thread hold,come with a screwHead hole diameter:4mmArm hole diameter:2mmMaximum Thickness: approx. 8mmArm Thickness: approx. 2mmMaximum Width: approx. 11mmTotal Length: approx. 30mmDistance from hole center to hole center：approx. 16mm,21mmColor: Gold Package Content:1pc x Aluminum Servo Arm with Screw .