I need help identifying parts

Thanks for your post. Your bi-fold door guide pins could be either our 21-054 that uses a locking cotter pin or our 21-078 using a locking push nut. The best way to decide which one would be to carefully compare yours to each of these parts. As for the top guide pin dropping out of the track, it may be missing a push nut or cotter pin. For that, see our 21-158 as well as our 21-155 for you to review. Lastly, for your nylinders, our 21-150 should work fine.