In Betaflight default configuration, the propellers spinning direction is like this. As show below, the M2 and M4 propellers are spinning to the inside direction of the quadcopter front.

But many piots would try another assemble method in reversed direction, as show below. As you could see, the M2 and M4 propellers are spinning to the outside of the drone head. So we also call it "props out".

Why Pilots Like "Props Out"

Many piltos who are flying a whoop drones will assemble their drone in the "props out" style in default, like the Alienwhoop ZER0, the BETAFPV Beta75X and Beta65X 2S Whoop drone etc.

Here is a video by BGUFF to show the difference between default Betaflight props direction and reversed props. 

Default Betaflight props direction, Quad dips and "washes out" in hard corners. With reversed props or "props out", no more dipping even in hardest cornering.

How to Setup a Props Out Drone

We will use a 2S whoop drone Beta65X for instance to show how to assemble and configure a "props out" drone.

1) Assemble the props correctly according to the "props out" style. CW props on the M2 and M3 motors and CCW props on the M1 and M4 motors. As show below.

2) Check the motors spinning direction in the Betaflight Configuration Motors Tab. Make sure the motors are spinning in the reversed direction (M2 and M3 are clock-wise and M1 and M4 are counter-clock-wise). If not, change the motors spinning direction accordingly in BLHeli Configuration.

3) Last, turn on the button of "Motor direction is reversed" in the Betaflight Configuration Tab. Don't forget the "Save and Reboot" button.