This is modified from another thingiverse carriage. It is perfect for the switchfector v3. I use it with titanium rods, and I use rubber bands (3 each side) to pull the rods into the magnets. Even at high speed and raised plastic it survives.Print qty 3. You need m3 bolts, and nuts for the rod ends, a long m3 screw to pull the third wheel against the rail. The nut for this goes in the back before you put on rail. Use pliers to insert. Put the two vwheels on one side, then put it on the vertical rail, then put the third wheel. As I use prethreaded rodes, I mounted the rod ends, and then screwed the rods into the ends. The other side of my rods have screw on balls.