These won't work well with smaller motors such as 1407's. 18xx or 22xx
Gemfan Flash Propellers have been specifically designed for high-speed racing. The inverse tip design helps to reduce blade tip vortex and the light weight of the propeller means it has a smaller moment of inertia and fast response time.
Gemfan designers use CATIA modeling software and Ansys Fluent to design their Flash propeller airfoils and blade style. Combining the most effective airfoils with different motors to get the most iterations on their design. Testing factors such as surface pressure, airfoil optimization, lift force, resistance, and torque have resulted in the Flash series - made just for racing.
Item name: flash 4052 3-blade propeller
Size: 4052, 4x5.2
Mounting hole: 5mm
Paddle size: 14mm
Hub thickness: 7.5mm
Suitable for 18-22 series motors
2x Gemfan Flash 4052 Durable 3 Blade CW
2x Gemfan Flash 4052 Durable 3 Blade CCW