The DJI 9.4x5 Self-Tightening Rotor (Thrust Boosted) is a set of two 9" propellers for the DJI Phantom 2 Vision Quadcopter. It features one clockwise (CW) and one counter-clockwise (CCW) rotating prop. Self-tightening design avoids prop becoming loose during operation and potentially flying away. The extra angle on these props enables them to take advantage of the extra power from the DJI Tuned Propulsion System.