The DJI Complete Frame Arm for S900 includes the frame arm, ESC, motor, props, and intermediate assembly hardware. There are four versions of the prop arm - depending on the stripe color (red or black), prop rotation (CW/CCW), and the ESC LED color (red/green). When replacing, it is crucial to select the exact same version of the prop arm as the original. This version features the black stripped arm, has a green ESC LED, and features counterclockwise (CCW) prop rotation.
The black, counter-clockwise (CCW) Frame Arm for S900 from DJI is an extension positioned between the main airframe the prop motor. When replacing the arm it is vital to use the same joint color and prop rotation designation (CW/CCW) as the original. The prop arms with red joints are the two that face toward the "nose", while those with black joints face the sides and tail.