Du-Bro Full Dual Servo Arm (For Hitec. Tower, Hobbico, Command) Part No: 3345. A servo arm for the pull-pull in large aircraft. This dual arm design allows for straight in-line movement. This super strong full arm includes 4-40 swivel ball links and hardware. There are four mounting positions and they are made from glass filled nylon for more strength. Dimension from center to the end mounting hole is: 1.5645" (39.75 mm)