Gemfan D51 Durable Propellers: Flight Optimization for FPV The Gemfan D51 Propellers (2020-4) are the perfect choice for FPV pilots and enthusiasts who are looking for improvements in flight performance. The four-blade design provides improved thrust and efficiency for both indoor and outdoor use. The 5.1-inch diameter offers a balance between power and control, ensuring stable and responsive steering in a variety of conditions. The durable construction ensures impact resistance, and the reduced noise helps in recording high-quality video materials. The set includes 8 pieces: 4 right-rotating and 4 left-rotating propellers.