The 5" frame is the industry standard sized quadcopter for freestyle and racing drones. They are referred to as 5" frames not because of the size of the frame itself, but the maximum size propeller that it can spin.
5" frames have been found to be the perfect medium between size and power. Larger frames tend to lose mobility and agility, while smaller frames struggle to have the same power, torque, and efficiency as their 5" counterparts.
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