This seemingly useless plate keeps your prop blades from folding over and crossing when you're using the attached prop hub. DO NOT 3D PRINT THAT PROP HUB!!!! YOUR PLANE WILL DIE!!!! It's just for reference. You may get it CNC machined if you like,.....do not sell the design please!! You can however print the stop plate. ABS, PETG, PLA,...your choice. Anything over 50% infill is fine.