2pcs Round Transparent Keyboard Stickers Russian Key Protector 1. Propellers specially made for Flip produce less noise and have undergone precise dynamic balancing tests to provide higher aerodynamic efficiency and powerful thrust to the aircraft. 2. Tips: Follow the instructions and attach propellers to the correct frame arms. When changing propellers, use the propellers in the same package. Do not mix propellers from different packages. 3. Diameter ?? Thread Pitch: 4.0 ?? 2.2 inch 4. Weight: 0.51 g Packing list: Propellers (pair) ?? 2 Screws ?? 12 (One propeller is composed of two blades with two screws. The front propellers on the left and right side of the aircraft are considered a pair of propellers, and the back propellors on the left and right are considered a second pair of propellors. When the Mini series propellors product listing mentions two pairs, it always refers to the pairing of the left and right front and the left and right back propellors, not the two blades that make up one propeller.)