These propellers are filled with carbon fibers that make the product stiffer than normal slow flyer propellers. The props will bearing less deformation under load, and hence result in a more linear and responsive throttle response.
GemFan produces excellent propellers for airplane and multirotor uses, and they are available in a variety of colors and materials. They are all well balanced from the factory and provide excellent and smooth power. You will not be disappointed with GemFan products on your aircraft.
Also included with the props are two sets of adapter rings that step down the center hole of the prop to allow it fit on different motor adapters and shafts. If you have a larger threaded shaft on your prop adapter, the center hole can be reamed out to a larger size as needed.
Note: This product contains 2 reverse rotation propeller as well as adapters in each package as you see in the product photo.