This is the buffer that the arm on the boot/trunk hits to stop it opening too far, if it cracks (which it will) then ultimately it tries to bend the gas struts.
Photo shows a broken one and the print.
This is for the RHS looking at the rear of the vehicle. The LHS is identical but mirror image.
Print this so it stands on the long edge (hole and pin are horizontal) or the the arm will seperate the layers, there is a lot of force there.
I used PETG at 100% infill.