ARX-R V2 frame is the fastest 5"/6" class quadcopter currently on the market. It is a beautiful piece of engineering that has been developed by Ryan at https://quadstardrones.com/
Flight videos of Ryan here : https://www.youtube.com/watch?v=T_NXj...
The kit provides an option to assemble a 6" true X quadcopter or a hybrid 5"/6".
Note: this frame has been purchased and was not provided for review. I am not affiliated to quadstardrones.