Have never broken any of these... And they help prevent tearing up the bottom plate. Half dome motor feet with two M3 size holes. Motor foot is wider than arm for added motor protection in crashes. Inside is hollow for weight savings. There are two different pieces for Front Left / Rear Right (FL-RR) and Front Right / Rear Left (FR-RL). This will account for the angle of the arms to keep the aerodynamics of the half dome forward. This mount is for those (like me) who install motors utilizing only two bolts/screws instead of four. The solid base will keep debris out of the otherwise open motor and arm holes. No supports needed. Printed at 0.3mm layer thickness at 10% infill.