Secraft Double-Lock Servo Arms are designed to clamp around and also make up for any inconsistencies in the servo output shafts. All arms are Heavy Duty Anodized Aluminum and tapped for 4-40 or M3 thread.

Secraft Double-Lock Servo Arms
Aluminum Servo Half Arm 1.25" (32mm)
Aluminum Servo Half Arm 1.5" (37mm)
Aluminum Servo Half Arm 1.75" (45mm)
Aluminum Servo Full Arm 2" (50mm)

Half arms are measured from the servo screw hole to the outside hole.

Note: Servo arms should fit snug, and not just slip onto the output shaft. In fact, they should go on a about a 1/3 of the way with light pressure and use the screw to pull them down the rest of the way. We do this because we are all after the tightest linkage and if there is any play in the spline fit it will only get worse. If need be, place a drop of light oil in the servo arm hole being very careful not to get any oil in the servo screw hole to help get the arm in place. Remember oil in the servo screw hole will not let the Loctite work properly. We suggest the arms will be installed outside the aircraft and on a stable flat surface.