For those who are using the excellent Donut prop-guard by ErgoFPV but ignored the instructions and printed them in normal TPU rather than the recommended NinjaTek Armadillo filament, then these protectors will allow you to safely transport the drone without worrying about deforming the guards.
In theory they could be used to straighten the guards out after a heavy impact.
Outer gaps between ducts allow for the drone to be strapped to a backpack or whatever.
Added a second version which can clip onto a Torvol Freestyle bag using the rubber bands on it.
Original TPU prop guards: https://www.thingiverse.com/thing:4040856