Phantom 2 props 8" vs 9"

[aclphoto]

I just noticed I have 2 different props for my P2...
I had ordered some extras and I asumme I ordered the 8 inch ones... I just tossed them in my repair kit and didn't notice it until today ( I got them a few days back)

Can anyone please explain the use of one or the other or both? I have a brand new Ps Non Vision H3-3D Gopro about 20 flights under my belt.

 

[rilot]

Stock props are 9" there's no good reason to change to 8" so stick with the stock ones.
DJI changed from 8" to 9" when the Vision was released.