The landing gear for the F550 & F450 that comes from DJI broke couple of days after installed them. Also the problem with the original DJI landing gear is that it is not foldable, so every time I had to remove them for travel. It is difficult to design a good landing gear (and foldable) that gets mounted on the bottom plate (I am still thinking on how to do that). In the mean time I looked online for landing gear for my F550, and found a few that get mounted on the arms, but not foldable! again.. difficult for transporting my F550. So I spent some time, and designed this foldable landing gear. One of the issues when I designed it, was how to make it stay folded or unfolded; the solution is simple... "R Clips" I designed it with 2 mm holes, for the R clip to insert when folded, or unfolded. I went to my local hardware store, and I could not find R Clips that matched perfectly, so I made my own from a wire coat hanger :) LOL The hole in the middle is 4 mm diameter. I used M4 screw 16 mm length; there is no need for the nut because it goes in by force, and it "creates" the thread in the top 3D printed piece. Usually 3D printers make holes smaller than design. But if you want piece of mind, I suggest to use a little longer screw (20 mm length), and use an M4 lock nut.Printer: Mendel90Rafts: NoSupports: NoResolution: 0.3Infill: 40%