GemFan produces some of the finest propellers for Multi-Rotor use, and they are available in a variety of colors and materials. All of the different sizes are available in both normal and reverse rotation as needed for use in multi-rotor craft. The High-Strength props are are made from Nylon with Carbon Fiber fill for an extremely stiff blade that will not deform under load. These props are about 10 times stiffer than the normal GemFan Multi-Rotor props. These special versions of the GemFan props have a 8mm hole with two flats molded in that are designed to fit the Stock DJI 2212-920 motors that come on the DJI Flamewheel 450 Quad and 550 Hex multirotor kits.