Summary I designed these props after breaking a few props,while learning to fly my QAV250. They are a good compromise between efficiency and printability. Print Settings Printer Brand: RepRap Printer: Prusa i3 Mini Rafts: No Supports: No Resolution: 0.2mm Infill: 100% Notes: Print them exactly how they are setup in the STL at 100% infill, once complete trim off the support material on the trailing edge of the blades. The support material may come off with your fingers or you may need scissors.Balance the props after post processing them and you should be good to go! They seem to do the trick for me and they use very little filament.