These propellers are filled with carbon fibers that make the product stiffer than normal slow flyer propellers. The props will bring less deformation under load, and hence result in a more linear and responsive throttle response. GemFan produces excellent propellers for airplane and multirotor uses. 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. Note: This product contains 4 normal rotation propellers and adapter rings in each package as you see in the product photo.